Potasser
Je vais potasser (piocher) un brin (students’ slang) = I’m going to swot (mug up) a bit.
Potin
Faire du potin (chambard, boucan) (pop.) = To kick up a row, a shindy.
Pouce
Manger sur le pouce = To take a snack.
Mettre les pouces = To give in, to knuckle under.
Lire du pouce (or, doigt) = To skip in reading (i.e. to do more work with the thumb than the brain).
Poudre
*Il n’a pas inventé la poudre = He will never set the Thames on fire.