A saying, phrase, idea, or action that randomly springs up in a class conversation that is echoed and used as a joke by the people in that class.
It is usually something that other classes will not understand and when mentioned in a group, only a small portion will get it.
Its basically an inside joke that the whole class gets.
"Cristina told a hot tub joke at lunch today, and all the med term kids cracked up while everyone else was confused at the classroom meme"
"Ty told Corey to 'square it' today in Algebra. Its a classroom meme"