the first event in a series
"she played Chopin for her opener"
"the season's opener was a game against the Yankees"
a person who unfastens or unwraps or opens
"children are talented undoers of their shoelaces"
a hand tool used for opening sealed containers (bottles or cans)
"He reached into his pocket to find an opener and pop the top off the soda can."
A person who opens something.
"The security guard acted as an opener by unlocking the heavy vault door at dawn."
In plain English: An opener is something used to start an activity, conversation, or game.
"The conversation started with an interesting story from his recent trip, which served as a perfect opener for everyone else to share their own experiences."
The word opener is formed by combining the verb open with the suffix -er to denote someone or something that performs the action of opening. It entered English directly from this straightforward construction without a shift in its core meaning.