overture

Short definition from Wiktionary

Noun

1. 1
   An opening; a recess or chamber.
2. 2
   Disclosure; discovery; revelation.
3. 3
   An approach or proposal made to initiate communication, establish a relationship etc.
4. 4
   A motion placed before a legislative body, such as the General Assembly of the Church of Scotland.
5. 5
   A musical introduction to a longer piece of music or a dramatic work (such as a play, an opera, or a motion picture).
6. 6
   A medley of themes from a larger work, such as an opera or musical, typically played at the beginning but sometimes played at any part of the work or performed as a standalone piece.

Verb

1. 1
   To make overtures; to approach with a proposal.

Adjective

1. 1
   Overt, that is, disclosed.