Lacking tact is a term used to describe someone who is not socially adept or polite. This can be seen in the crossword solutions for the term, such as 'CRUDE, ' which means lacking in refinement or delicacy; 'classless, ' which means having no sense of propriety; 'BRASH, ' which means impudent and bold; 'RUDE, ' which means discourteous and disrespectful; 'GAUCHE, ' which means awkward and lacking in social graces; and 'INDISCREET, ' which means not showing good judgement or discretion.