Cos'è declare? Cos'è declare? To make known formally or officially. See Synonyms at announce.To state emphatically or authoritatively; affirm.To reveal or make manifest; show. To make a full statement of (dutiable goods, for example).Games To designate (a trump suit or no-trump) with the final bid of a hand in bridge.To make a declaration.To proclaim one's support, choice, opinion, or resolution.declare war To state formally the intention to carry on armed hostilities against.declare war To state one's intent to suppress or eradicate: declared war on drug dealing in the neighborhood.