1 not used before a noun : attached to or covering something
▪ The lid is on tight. 2 not used before a noun : performing or speaking in public
▪ The band will be on in 10 minutes. ▪ Mr. President, you are on in two minutes. [=you will be giving your speech in two minutes] 3 not used before a noun : working at a job
▪ He is on tomorrow from 6 a.m to 6 p.m. 4 a not used before a noun : operating or flowing
▪ The radio/water/electricity is on.
b : in a position that starts the flow of electricity, water, etc.
▪ The switch is on. ▪ The lever is in the on position. 5 not used before a noun a : taking place or happening
▪ The deal/game is on. ▪ (Brit) We do not have anything on [=planned] this weekend.
b : doing something as planned
▪ Are we still on for dinner tomorrow? [=are we still having dinner tomorrow, as we planned to do?] 6 not used before a noun : being broadcast on television or radio
▪ The show is on at 8 p.m. ▪ The game is on tonight. ▪ My favorite show is on. 7 not used before a noun, chiefly US — used to say that you are able to do something well at a particular time ▪ My golf game was off yesterday, but it/I was on today. [=I played well today]