(linguistics) A term formed from the initial letters of several words or parts of words, which is itself pronounced letter by letter.

plural of initialism

The act of initiating, or the process of being initiated or introduced

A new member of an organization. / One who has been through a ceremony of initiation. / One who is oriented in and familiar with a topic or subject, especially one who is expert in it.

(transitive) To begin; to start. / To instruct in the rudiments or principles; to introduce. / To confer membership on; especially, to admit to a secret order with mysterious rites or ceremonies.

(obsolete) Unpractised; untried; new. / (obsolete) Begun; commenced; introduced to, or instructed in, the rudiments; newly admitted.

At the beginning.

Chronologically first, early; of or pertaining to the beginning, cause or origin. / Spatially first, placed at the beginning, in the first position; especially said of the first letter of a word.

The first letter of a word or a name. / In plural, the first letter of each word of a person's full name considered as a unit.

(transitive) To sign one's initial(s), as an abbreviated signature.