The Collaborative International Dictionary
Intumescing
Intumesce \In`tu*mesce"\, v. i. [imp. & p. p. Intumesced; p. pr. & vb. n. Intumescing.] [L. intumescere; pref. in- in + tumescere to swell up, incho. fr. tumere to swell. See Tumid.] To enlarge or expand with heat; to swell; specifically, to swell up or bubble up under the action of heat, as before the blowpipe.
In a higher heat, it intumesces, and melts into a
yellowish black mass.
--Kirwan.