Source : Webster's Revised Unabridged Dictionary (1913)

Lignify \Lig"ni*fy\ (-f[imac]), v. t. [imp. & p. p. {Lignified}
   (-f[imac]d); p. pr. & vb. n. {Lignifying} (-f[imac]`[i^]ng).]
   [L. lignum wood + -fy: cf. F. lignifier.] (Bot.)
   To convert into wood or into a ligneous substance.

Lignify \Lig"ni*fy\, v. i. (Bot.)
   To become wood.