Definitions
1.VerbTo erect; to construct.
2.VerbTo close up by building."to build up a door"
3.VerbTo accumulate: to increase incrementally or continually."Ever since the secretary left, the letters in my inbox have started to build up."
4.VerbTo strengthen."They had to build up their fortress to protect against attack."
5.VerbIn solitaire card games, to place a card over another card of lower value. (e.g., place 5♦ over 4♣)
6.NounMisspelling of buildup.