To be “thirsty” is to desperately want approval. Its been linked to the 1936 work of a scientist, but uh, it’s more frequently used on the internet, with variations appearing since 2010. Missy Elliott’s “Chinga-A-Ling” and other hip-hop songs helped popularize it. Used in a sentence: “Don’t like all of their Instagram posts. It’ll make you look thirsty.”