Someone who is punctilious is very careful to behave correctly. He was punctilious about being ready and waiting in the entrance hall exactly on time He was a punctilious young man. + punctiliously punc·tili·ous·ly Given the circumstances, his behaviour to Laura had been punctiliously correct. very careful to behave correctly and follow rules punctilious about (punctilio (16-21 centuries), from puntiglio, from puntillo, from punctum; POINT)