Expressionless is a related term of rumbling.
As adjectives the difference between expressionless and rumbling
is that expressionless is without expression while rumbling is deep and slow sounding.
As a noun rumbling is
the sound of complaint.
As a verb rumbling is
.
rumbling
English
Adjective
(
en adjective)
Deep and slow sounding.
:His rumbling voice fit the solemn occasion.
Noun
(
en noun)
The sound of complaint.
:The rumblings of the masses precedes the crumbling of the state.
A deep low noise.
:The rumbling of distant thunder.
Verb
(head)