When referring to a man's
erection as a boner, a boner shrinker would be anything that diminishes it. Most likely an unattractive woman. Made famous by the 9/
13/2008 opening skit of Saturday
Night Live dialog by Tiny Fey and Amy Poehler:
FEY AS PALIN: "So we ask reporters and commentators,
stop using
words that diminish us,
like 'pretty,' 'attractive,' 'beautiful.'"
POEHLER AS CLINTON: "'Harpy,' 'shrew' and 'boner shrinker.'"