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