it's pretty common knowledge at this point that gyaru girls have their own sort of lingo. i won't spend too much time explaining it- mostly because i don't know how to explain the concept of a dialect- but they basically will shorten words/phrases, or add suffixes to words, for the purpose of sounding more... unique, i suppose? i'm actually not too sure about the purpose. i do know that i find it very funky and fun, so here's some terms you can learn, and some substitutes that i would use in english (as well as words i personally use that i think fit in with gyaru slang.)
common gyaru words!
poyo - poyo is a suffix that sounds cute, and it can be added onto any word, really. (rabupoyo is to be in love. sagepoyo is to be sad, or disappointed. shogepoyo is to be bored.) the most common use of this suffix is agepoyo, which is used to convey happiness and excitement. ("i just got the cutest skirt! agepoyo!")
an english term that could replace poyo could be -dom. you could say things like, "oh, i just passed my test! total hapdom!" to signify that you're happy. "saddom" to signify that you're sad, "scaredom" to signify that something is scary, "lovedom" to say you're in love, etc.
oolong cha - a term used for annoying, long-haired office workers. since gals have all different types of hair, catergorizing a "normie" by their typical/standard/boring long hair would make sense.
long-hair is a term in english, though it's meaning is different, generally used to refer to hippies or alt men who grow out their hair. a term i would use to replace this would be a suit. for example, "that karen is a total suit!" or "i hate all these dumb suits!"
yarirafii - this one was papillon magazine's "most used gyaru term" in 2020! it stands for someone who is super energetic, and became mostly associated with guys who wear tight shirts and pants and who dance to energetic music.
this term being mainly used for men actually makes it harder to determine an english substitute. my personal association with men in tight shirts and skinny jeans is emo boys or punk rockers, so a possible substitute could be punker. other more general terms could be fireball, whizz-kid, or live-wire. ex., "he's a total live-wire!" or "that punker was so cool, right?"
hanya - this was made popular by, to quote papillon magazine, "YouTuber Maruyama Rei [who] plays the character Inoue Chiaki who is the manager of the High Schools Art Club, [and] this character of hers often says this." it's a term you would use when you don't understand something, or are trying to convey confusion.
this one could be replaced with something like "hah?" or "whut," though if you were looking to replace it with a word, there isn't really one. closest we could get would be something like "whassat/whatsit?" which is more like combining two words.
words with simple translations!
atonsu - meaning thank you, but not as professional (?) as "arigatou." think "thanx!" rather than "thank you."
pachikoku - this is the action of telling a lie, so the most direct translation would be "lying." to add spice, simply remove the g. "i was totes lyin'!"
kamitteru - literally means god-like. for example, "that makeup is totally god-like!" given that this is also a term in english, i won't try and come up with a replacement, LOL.
kyun desu - meaning heart-throb, it comes from "kyunkyun," which is a heart throbbing. this is another tyerm that already exists in english, so no need for a sub.
ieiiei - this one feels obvious, but it just means "yayay." good for exclaiming your happiness!
daijyobu-sou - this is a way of asking if something looks okay. you could simply ask "lookin' good?" if you felt like spicing it up. i personally don't see myself using this one much, LOL.
tobu-zo - this one i WILL be using tons! it's a term for when something is really delicious. a good easy substitute would be "totes yummy," or "crazy yummy!" you could even say "yums" if you felt like it.
uku-zo - the term "uku" means to float, so this is generally used to say "i'm so happy i'll float!" you could always say "i'm flying" or "i'm floating" as your replacement.
english gal terms!
please note that, to my knowledge, there's no real "official" gyaru slang in english. these are just terms i personally use that i felt fit in with gal terms! i promise i'll add more as i think of more, but these were the ones i could think of for now.
megs/totes - megs is a prefix i use for when something is ultra-thing. i don't think it's too uncommon to hear people say something is "mega bad/good/etc.," but i feel like turning it from mega into megs gives it a bit more flavour! totes is much more commonly used, but it's a classic.
yuh - yuh is just a sort-of short and megs-casual way to say yes, which i generally use when i'm excited. an extremely common occurance is someone asks me if i want something, and then i respond "yuh!" while pumping my fists.
dorbs - short for "adorbs," which is short for "adorable," this describes something that is just that- totes-megs-adorable. i actually don't use this one as often as i wish i did, ugh.
rock - this is actually one me and my friend came up with as a joke, but i really unironically love it. they had said "that's rock, even," and explained it as being like how people will say "that rocks." we had a laugh about it, but i genuinely love it. you could see some super pretty lipstick and think "that's rock!"
prommy - simply put, this is short for promise. "prommy i won't do it!"
whatev - another simple one, short for whatever. "i don't like it, but it's whatevs."