[n] the small unused part of something (especially the end of a cigarette that is left after smoking)
[n] the part of a check that is retained as a record
[n] a torn part of a ticket returned to the holder as a receipt
[n] a small piece; "a nub of coal"; "a stub of a pencil"
[n] a short piece remaining on a trunk or stem where a branch is lost
[v] strike against an object, as of one's toe or foot