kickoff vs showtime

kickoff and showtime both are nouns.

Word	Noun	Adjective	Verb	Adverb
kickoff	Yes	No	No	No
showtime	Yes	No	No	No

As nouns, kickoff and showtime are synonyms defined as:

Other synonyms of kickoff include beginning, commencement, first, get-go, offset, outset, start, starting time.

kickoff (noun)	showtime (noun)
(football) a kick from the center of the field to start a football game or to resume it after a score	the time at which something is supposed to begin
a start given to contestants
the time at which something is supposed to begin