(programming) To reclaim resources which are no longer in use; to run a garbage collector.

(grammar) A noun which, though singular, refers to a group of things or animals. Examples: a school of fish, a pride of lions.

(US) To make a telephone call in which the cost of the call is paid by the person receiving the call.

The hobby of collecting and displaying postage stamps and related items. / (figuratively, usually derogatory) Collection of items or information of no intrinsic value.

(idiomatic) To remain untouched and unused for a long period of time.

plural of collective noun

(psychology) The common experiences, thoughts and opinions of a large group of people taken as a whole.

The concept of maintaining peace among all nations or members of a group by making the security concerns of one member important to all members.

plural of type collection

A contract specifying terms and conditions of employment between one or more labour unions and employers' associations legally binding for employers organized in these and the employees if they are unionized in them or their employment contract incorporates them by referral.