The Collaborative International Dictionary of English v.0.48:
Certitude \Cer"ti*tude\, n. [LL. certitudo, fr. L. certus: cf. F. certitude. See Certain.] Freedom from doubt; assurance; certainty. --J. H. Newman. [1913 Webster]WordNet (r) 3.0 (2006):
certitude n 1: total certainty or greater certainty than circumstances warrant [syn: certitude, cocksureness, overconfidence]