knock something off—
1. make smth. fall with a push:
- Just when I put the glass safely down on the table, the cat jumped up and knocked it off.
2. (coll.) write smth. quickly and carelessly:
- He could knock off a poem in half an hour.
3. (coll.) put a work out of hand; complete smth.:
- I’ve a pile of work to knock off before I can take my holiday.
4. (coll.) discontinue smth.; give up (work):
- He at once knocked off painting for the day.
5. (sl.) steal smth.:
- Where did he get all those watches? Did he knock them off?
knock something out—
1. remove smth. with a sharp blow:
- Knock the ash out before you refill your pipe.
2. destroy smth. completely:
- Our soldiers had orders to knock out the enemy guns.
3. (coll.) play music roughly or unskillfully:
- He can’t read music but he can knock out a tune on the piano.