low blow

noun

1. (in boxing) an illegal blow below the waist of an opponent.

2. an unfair or unsportsmanlike criticism or attack.

Word History and Origins

Origin of low blow¹

First recorded in 1950–55

Idioms and Phrases

An unscrupulous attack; an insult. For example, When my roommate moved out without a word of warning, leaving me to pay the entire rent, that was a low blow, or She wanted to win the argument, but bringing up his failed marriage was a low blow. This term alludes to the illegal practice of hitting an opponent in boxing below the belt. [c. 1950]