The Collaborative International Dictionary of English v.0.48:

Diffract \Dif*fract"\, v. t. [imp. & p. p. Diffracted; p. pr.
   & vb. n. Diffracting.] [L. diffractus, p. p. of diffringere
   to break in pieces; dif- = dis- + frangere to break. See
   Fracture.]
   To break or separate into parts; to deflect, or decompose by
   deflection, a? rays of light.
   [1913 Webster]

WordNet (r) 3.0 (2006):

diffract
    v 1: undergo diffraction; "laser light diffracts electrons"