We don't have synonyms for untap yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are uncap, unta and unhap.
(v) :
(board games, card games) Opposite of tap; to return (transitive) a card or piece, or (intransitive) all available cards or pieces, to their original orientation (e.g. at the start of a new turn) to indicate that they are ready to be used again.
(v) :
(transitive, nonstandard) To release a flow of (creativity, potential, etc.); to unleash.
(v) :
(board games, card games) Opposite of tap; to return (transitive) a card or piece, or (intransitive) all available cards or pieces, to their original orientation (e.g. at the start of a new turn) to indicate that they are ready to be used again.
(v) :
(transitive, nonstandard) To release a flow of (creativity, potential, etc.); to unleash.