- an erection of the penis.
Origin of hard-on
First recorded in 1890–95
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for hard-on
Just the hard-on before you shoot unarmed members of the public.'Babylon' Review: The Dumb Lives of Trigger-Happy Cops
January 9, 2015