Popular Phrase
Catchphrase, Popular Word, Buzzword
You know that 流行 means "trend", so "trend" language means a popular phrase. Yolo! It could also be a catchphrase, a popular word, or a buzzword.
りゅうこうご
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
どの流行語が、今年の流行語大賞にえらばれると思う？
Which popular phrase do you think will be chosen for this year's buzzword of the year?
毎年ほんとに色んな流行語が生まれるよね。
A lot of new catchphrases are born every year, huh?
ここ数年の間に、「ミーム」はインターネットでの流行語となりました。
In the past few years, "meme" has become a popular word on the internet.