Source : Webster's Revised Unabridged Dictionary (1913)

Tactless \Tact"less\, a.
   Destitute of tact.

Source : WordNet®

tactless
     adj 1: lacking or showing a lack of what is fitting and considerate
            in dealing with others; "in the circumstances it was
            tactless to ask her age" [syn: {untactful}] [ant: {tactful}]
     2: showing skill in handling difficult situations [syn: {undiplomatic}]
     3: revealing lack of perceptiveness or judgment or finesse; "an
        inept remark"; "it was tactless to bring up those
        disagreeable" [syn: {inept}]