Source : Webster's Revised Unabridged Dictionary (1913)

Pugnacious \Pug*na"cious\, a. [L. pugnax, -acis, fr. pugnare to
   fight. Cf. {Pugilism}, {Fist}.]
   Disposed to fight; inclined to fighting; quarrelsome;
   fighting. --{Pug*na"cious*ly}, adv. -- {Pug*na"cious*ness},
   n.

Source : WordNet®

pugnaciously
     adv : in a pugnacious manner