1 (so as to be) supported by or attached to or covering or enclosing (sat on a chair; stuck on the wall; rings on her fingers; leaned on his elbow).
2 carried with; about the person of (have you a pen on you?).
3 (of time) exactly at; during; contemporaneously with (on 29 May; on the hour; on schedule; working on Tuesday).
4 immediately after or before (I saw them on my return).
5 as a result of (on further examination I found this).
6 (so as to be) having membership etc. of or residence at or in (she is on the board of directors; lives on the continent).
7 supported financially by (lives on pound50 a week; lives on his wits).
8 close to; just by (a house on the sea; lives on the main road).
9 in the direction of; against.
10 so as to threaten; touching or striking (advanced on him; pulled a knife on me; a punch on the nose).
11 having as an axis or pivot (turned on his heels).
12 having as a basis or motive (works on a ratchet; arrested on suspicion).
13 having as a standard, confirmation, or guarantee (had it on good authority; did it on purpose; I promise on my word).
14 concerning or about (writes on frogs).
15 using or engaged with (is on the pill; here on business).
16 so as to affect (walked out on her).
17 at the expense of (the drinks are on me; the joke is on him).
18 added to (disaster on disaster; ten pence on a pint of beer).
19 in a specified manner or style (often foll. by the + adj. or noun: on the cheap; on the run).
1 (so as to be) covering or in contact with something, esp. of clothes (put your boots on).
2 in the appropriate direction; towards something (look on).
3 further forward; in an advanced position or state (time is getting on; it happened later on).
4 with continued movement or action (went plodding on; keeps on complaining).
5 in operation or activity (the light is on; the chase was on).
6 due to take place as planned (is the party still on?).
7 colloq. a (of a person) willing to participate or approve, or make a bet. b (of an idea, proposal, etc.) practicable or acceptable (that's just not on).
8 being shown or performed (a good film on tonight).
9 (of an actor) on stage.
10 (of an employee) on duty.
11 forward (head on).
—adj. Cricket designating the part of the field on the striker's side and in front of the wicket.
—n. Cricket the on side.
Phrases and idioms:
be on about refer to or discuss esp. tediously or persistently (what are they on about?). be on at colloq. nag or grumble at. be on to
1 realize the significance or intentions of.
2 get in touch with (esp. by telephone). on and off intermittently; now and then. on and on continually; at tedious length. on-line Computing (of equipment or a process) directly controlled by or connected to a central processor.
1 (of a switch) having two positions, 'on' and 'off'.
2 = on and off. on-stage adj. & adv. on the stage; visible to the audience. on-street (with ref. to parking vehicles) at the side of a street. on time punctual, punctually. on to to a position or state on or in contact with (cf. ONTO).
Etymology: OE on, an f. Gmc
Useful english dictionary. 2012.