a fortiori UK /ˌeɪ ˌfɔːɹtiˈɔːɹaɪ/US /ˌeɪ ˌfoɹʃiˈoɹˌaɪ/adjective 1adverb 1forms 2 adjective1 •(rhetoric) With stronger or greater reason; as a corollary implied by a stronger claim; even more so; all the more so; so much the more. adverb1 •(rhetoric) With stronger or greater reason; as a corollary implied by a stronger claim.Now starting and stopping cannot themselves have starts or stops, or, a fortiori, middles either. — 1954 formsmore a fortiori · most a fortiori