Someone or something that concludes.
Someone or something that closes.
Synonym of close (“the point at the end of a sales pitch when the consumer is asked to buy”)
The last stone in a horizontal course, if smaller than the others; a piece of brick finishing a course.
A relief pitcher who specializes in getting the last three outs of the game. See Wikipedia:closer (baseball)
Something that prevents the completion, or ends the existence, of a project etc.; a fatal setback.
A strike or blow that leads to death, especially a coup de grace.