cheap shot

n.
An unfair or unsporting verbal attack on a vulnerable target.

(cheep shot)

noun
1. An act of intentional roughness against an opponent, especially in a contact sport.
2. An unsportsmanlike remark or action directed at a known weakness of another.

Usage
"We don't care if he's Time magazine's 'Person of the Year' or not, that was a cheap shot New York Mayor Rudolph Giuliani took at Boston and its police." — Editorial: Rudy Giuliani Shows Skin Still Very Thin; The Boston Herald; Dec 29, 2001.

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An unfair or unsporting verbal attack, as in You called him an amateur? That's really taking a cheap shot. The term originated in sports, especially American football, where it signifies deliberate roughness against an unprepared opponent. [Slang; second half of 1900s]

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