ungentlemanly adjective 1adverb 1forms 2 adjective1 •Not gentlemanly; not adhering to the high moral standards expected of a gentleman; impolite, unchivalrous, or indecent.My grandmother thought it was ungentlemanly of my boyfriend to suggest that we split the bill for dinner. adverb1 •In a manner not befitting a gentleman. formsmore ungentlemanly · most ungentlemanly