We don't have synonyms for count in yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are mountain, contain and fountain.
(v) :
(transitive) To include (someone) in an activity, etc.
(v) :
(transitive) To do a countdown before the start of something, especially a musical performance, in which case the countdown is in time with the beats of the music.
(v) :
(transitive) To include (someone) in an activity, etc.
(v) :
(transitive) To do a countdown before the start of something, especially a musical performance, in which case the countdown is in time with the beats of the music.