This paper characterizes grammars generating Spanish sentences of imprecise meaning. The basic grammar generating sentences onforming to the standard paradigm of fuzzy logic (Quantifier + Noun + Verb + Modifier + Adjective) is systematically deformed (by inversion, suppression or addition of nonterminal elements in its production rules) to produce a series of grammars generating grammatical, semantically acceptable semigrammatical or ungrammatical sentences.