Source : Webster's Revised Unabridged Dictionary (1913)

Snicker \Snick"er\, v. i. [imp. & p. p. {Snickered}; p. pr. &
   vb. n. {Snickering}.] [Cf. D. snikken to sob, to sigh.]
   [Written also {snigger}.]
   1. To laugh slyly; to laugh in one's sleeve.

   2. To laugh with audible catches of voice, as when persons
      attempt to suppress loud laughter.