"Sell like hotcakes" and "call it a day," for example (6)
I believe the answer is:
idioms
(Other definitions for idioms that I've seen before include "Sayings with meanings not obvious from the words" , "Characteristic modes of expression" , "Expressions" , "Group of words having a meaning not obvious from the words e.g over the moon" , "Characteristic styles of expression, language or art" .)