Definify.com
Webster 1913 Edition
Glum
Glum
,Adj.
 Moody; silent; sullen. 
I frighten people by my 
 glun 
face. Thackeray.
Glum
,Verb.
 I.
 To look sullen; to be of a sour countenance; to be glum. 
[Obs.] 
Hawes.
 Webster 1828 Edition
Glum
GLUM
,Adj.
  GLUM
,Noun.
  Definition 2025
Glum
glum
glum
English
Verb
glum (third-person singular simple present glums, present participle glumming, simple past and past participle glummed)
-  (obsolete) To look sullen; to be of a sour countenance; to be glum.
- (Can we find and add a quotation of Hawes to this entry?)
 
 
Noun
glum (uncountable)
-  (obsolete) sullenness
- (Can we find and add a quotation of Skelton to this entry?)
 
 
Etymology 2
Probably from Middle Low German glum (“glum”), related to German dialectal glumm (“gloomy, troubled, turbid”). More at gloomy.
Adjective
glum (comparative glummer, superlative glummest)
-  despondent; moody; sullen
-  Thackeray
- I frighten people by my glum face.
 
 
 -  Thackeray