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1. knock one off
To have sex or at least reach orgasm in a restricted amount of time.
When I wake up in the morning the gf and me knock one off before I go to work.
by gerf Jun 4, 2004 add a video
2. knock one off
1. Make love to yourself
2. A bout of self help
3. To masterbate
4. Pull the popes cap off

Dont go to the shop yet sugar, I just need to quickly knock one off.
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