Forever Hold
When you call someone that doesn't want to talk to you, they put you on hold forever so you will eventually hang up.
I hate my phone company. I called customer service and they put me on forever hold. They played showtunes so loud, I had to hang up!
Speak Now or Forever Hold Your Penis
When a hot girl is about to go get it on with some other dude and you basically have to act right now before the window of opportunity closes
Dude, The hottest girl in the club's about to leave with that chad over there. Speak Now or Forever Hold Your Penis!
Speak now, or forever hold your piece
Refers to where da irate "paw" of a redneck chick is permitted only one opportunity to protest a horny stud's getting his "little pumpkin" preggo before he is permanently barred from demanding a shotgun wedding.
In da infamous "history of da yodel" tale, da enraged farmer unwittingly missed his single chance at recourse against da nameless traveler who had "gotten it on in da hayloft" with both his daughter AND his wife da night before --- said sly seed-spreader simply "had his fun" and then quietly slipped off far away before da man even knew what had happened --- and thus said furious family-head was made a victim of da old "Speak now, or forever hold your piece" scenario.