(in boxing) an illegal blow below the waist of an opponent.
2.
an unfair or unsportsmanlike criticism or attack.
Origin
1950-55
Slang definitions & phrases for low blow
low blow
noun phrase
An unfair and malicious stroke; cheap shot: ''They'd be rendered mute if they couldn't use sports analogies.'' ''Low blow, Alice''
[1940s+; fr the illegal blow below the belt in boxing]
Idioms and Phrases with low blow
low blow
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 ]