The Collaborative International Dictionary of English v.0.48:

Knightly \Knight`ly\, a. [AS. cnihtlic boyish.]
   Of or pertaining to a knight; becoming a knight; chivalrous;
   as, a knightly combat; a knightly spirit.
   [1913 Webster]

         For knightly jousts and fierce encounters fit.
                                                  --Spenser.
   [1913 Webster]

         [Excuses] full knightly without scorn.   --Tennyson.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Knightly \Knight"ly\, adv.
   In a manner becoming a knight.
   [1913 Webster]

         And why thou comest thus knightly clad in arms. --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

knightly
    adj 1: characteristic of the time of chivalry and knighthood in
           the Middle Ages; "chivalric rites"; "the knightly years"
           [syn: chivalric, knightly, medieval]
    2: being attentive to women like an ideal knight [syn:
       chivalrous, gallant, knightly]

Moby Thesaurus II by Grady Ward, 1.0:

67 Moby Thesaurus words for "knightly":
   aristocratic, big, bighearted, bold, bold-spirited, brave,
   ceremonious, chivalric, chivalrous, courageous, courtly, doughty,
   ducal, elevated, exalted, formal, gallant, generous, genteel,
   gentle, gentlemanlike, gentlemanly, great, great of heart,
   greathearted, handsome, hardy, heroic, herolike, high, high-minded,
   idealistic, intrepid, ironhearted, kinglike, kingly, knightlike,
   ladylike, largehearted, liberal, lionhearted, lofty, magnanimous,
   manful, manly, noble, noble-minded, of gentle blood, of rank,
   old-fashioned, old-world, openhanded, patrician, princelike,
   princely, queenlike, queenly, quite the lady, soldierlike,
   soldierly, stalwart, stout, stouthearted, sublime, titled, valiant,
   valorous