Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ūrīgo, ĭnis, f. [uro], lustful heat, desire, pruriency (post-class.), App. M. 8, p. 215, 16; 1, p. 105, 27; Arn. 5, 187 (but in Plin. 20, 22, 87, § 238, the correct read. is ustio).