Source : Webster's Revised Unabridged Dictionary (1913)

Inattentive \In`at*ten"tive\, a. [Cf. F. inattentif.]
   Not attentive; not fixing the mind on an object; heedless;
   careless; negligent; regardless; as, an inattentive spectator
   or hearer; an inattentive habit. --I. Watts.

   Syn: Careless; heedless; regardless; thoughtless; negligent;
        remiss; inadvertent. -- {In`at*ten"tive*ly}, adv. --
        {In`at*ten"tive*ness}, n.

Source : WordNet®

inattentive
     adj 1: showing a lack of attention; "inattentive students" [ant: {attentive}]
     2: inattentive because of lack of interest
     3: not showing due care or attention; "inattentive students";
        "an inattentive babysitter"; "neglectful parents" [syn: {neglectful}]
     4: unwilling to hear [syn: {unheeding}, {unlistening(a)}, {deaf
        to(p)}]
     5: not paying attention [syn: {unobservant}, {unvigilant}, {unwatchful}]