The Collaborative International Dictionary of English v.0.48:

Lignification \Lig`ni*fi*ca"tion\
   (l[i^]g`n[i^]*f[i^]*k[=a]"sh[u^]n), n. [Cf. F. lignification.
   See Lignify.] (Bot.)
   A change in the character of a cell wall, by which it becomes
   harder. It is supposed to be due to an incrustation of
   lignin.
   [1913 Webster]