Kusa

In Japanese internet culture, "w" (short for warai = laugh) is used like "lol." When people spam it — "wwwww" — it looks like grass growing, so 草 (kusa, meaning grass) became slang for laughing. It evolved further: 草生える (kusa haeru = "grass is growing") means "that is hilarious," and 大草原 (daisougen = "vast grasslands") means you are absolutely dying laughing. Now everywhere on social media and has even crept into spoken conversation, with young people literally saying "kusa" out loud. Some have escalated beyond grass to 竹 (bamboo) and 森 (forest) for even bigger laughs. Used more in text messages and online chat than in spoken conversation.