o·pen·er 
(ōpə-nər)
(ōpə-nər)n.
Idiom: 1. One that opens, especially a device used to cut open cans or pry up bottle caps.
2. Games
a. The player who starts the betting in cards.
b. openers Cards of sufficient value to enable the holder to open the betting.
3. A remark that initiates a conversation.
4.
a. The first act in a program of entertainment, as in a theatrical variety show or a concert.
b. Any act in a program of entertainment that takes place prior to the main act, as in a theatrical variety show or a concert.
5. Sports The first game in a series.
for openers Informal
To begin with: "Out of 54 potential jurors, they knocked 20 off ... just for openers" (Joseph DiMona).