intransitive. To have a common part or share of something; to partake, participate, or share with or in something.

to take part: †(a) to share or partake (in, of, or with) (obsolete); (b) to participate (in). Cf. senses 10a, 11.

intransitive. To talk together, converse with someone; to communicate; to confer, consult. Also with of, upon and on. Now rare (archaic in later use).

intransitive. To participate.

intransitive. To take part; to have a part or share with a person, in (formerly also †of) a thing; to share. Cf. partake, v. 1b.

with const. To associate oneself or take part in an action, or to do something.

intransitive. With in. To take a part or share in an action, circumstance, or situation; to have a part in or portion of something in common with…

to bear a part: (a) to take part, share, participate in; †(b) to play a part as an actor or actress (obsolete).

intransitive. To share or participate with others, or mutually. (Cf. common, v. 1b) Obsolete.

also absol. to join in (the action being understood from the context).

to be in it: to be one of those actually engaged as partners, competitors, etc. Now Australian.

intransitive. colloquial. Chiefly with with. To share or participate in an activity, enterprise, etc.

Originally U.S. to get into (also in on) the act and variants: to become a participant; to involve oneself in some advantageous venture or activity.

(to be) in on the act: (to be) involved in some advantageous venture or activity.

intransitive. colloquial. Originally: to share rations. Later: to share food, facilities, etc. (with); to tuck in to food; to participate or…

intransitive. to opt in: to choose to participate in something.