on

be on about talk about tediously and at length. British informal

be on at someone nag or grumble at someone. British informal

be on to someone be close to discovering the truth about an illegal or undesirable activity that someone is engaging in. informal

be on to something have an idea or information that is likely to lead to an important discovery. informal

it's not on it's impractical or unacceptable. informal

on and off intermittently; now and then.

on it drinking heavily. Australian informal

on side supporting or part of the same team as someone else.

2001Daily Telegraph In Oman, the policy of getting the local population on side was taken further, with the rebels who fought for the communists progressively being turned to fight against them.

what are you on? said to express incredulity at someone's behaviour, with the implication that they must be under the influence of drugs. informal

you're on said by way of accepting a challenge or bet. informal