Source : Webster's Revised Unabridged Dictionary (1913)

Knight bachelor \Knight" bach"e*lor\; pl. {Knights bachelors}.
   A knight of the most ancient, but lowest, order of English
   knights, and not a member of any order of chivalry. See
   {Bachelor}, 4.

Source : WordNet®

knight bachelor
     n : a knight of the lowest order; could display only a pennon
         [syn: {bachelor-at-arms}, {bachelor}]