opener

Short definition from Wiktionary

Noun

1. 1
   A person who opens something.
2. 2
   A device that opens something; specifically a tin-opener/can-opener, or a bottle opener.
3. 3
   An establishment that opens.
4. 4
   The player who starts the betting.
5. 5
   Cards of sufficient value to enable a player to open the betting.
6. 6
   A person employed to separate sheets of hot metal that become stuck together.
7. 7
   The first act in a variety show or concert.
8. 8
   A batsman or bowler who normally plays in the first two positions of an innings.
9. 9
   The first in a series of events, items etc.; the first remark or sentence of a conversation.
10. 10
    The first game played in a competition.
11. 11
    The first goal or point scored.
12. 12
    A period of time when it is legal to commercially fish.
13. 13
    A pitcher who specializes in getting the first outs of a game before being replaced, either by a long reliever or a pitcher who would normally start.

Adjective

1. 1
   comparative form of open: more open