go-ahead

Short definition from Wiktionary

Noun

1. 1
   Approval, agreement, or instruction to begin or proceed.
2. 2
   A flip-flop (footwear).

Adjective

1. 1
   Progressive; exerting leadership.
2. 2
   Dashing; energetic.
3. 3
   Being a score which gives the scoring team or player the lead in the game.

Verb

1. 1
   To proceed with; to begin.
2. 2
   Used to grant permission for or to give endorsement of a suggestion or proposal.
3. 3
   To send communication over the radio.