lengthy, long, prolonged
brief, momentary, a moment's, short
There was a moment's silence before she replied.

deep, hushed
awed
We sat and watched in awed silence as she performed.

absolute, complete, dead, deadly, deathly, total, utter
We sat in complete silence, save for the ticking of the clock.
A deathly silence hung over the town.

relative
The rest of the trip passed in relative silence.

shocked, stunned
Her comments were met with a stunned silence.

awkward, embarrassed, embarrassing, strained, uncomfortable, uneasy
An awkward silence followed.

heavy, ominous, oppressive, tense
brooding, thoughtful
She fell into long, brooding silences.

stony, sullen
eerie, unnerving
companionable
They walked in companionable silence.

expectant, pregnant
sudden
radio
The soldier had broken radio silence to contact his aircraft.

moment

maintain
She maintained a stony silence.

break, interrupt, penetrate, pierce, punctuate, shatter
Lewis finally broke the long silence between them.
Celeste's voice penetrated the silence.
a silence punctuated only by the occasional sniff from the children

lapse into, relapse into, retreat into, subside into, trail off into (all used only about people)
He lapsed into a sullen silence.

stun sb into
The boys were stunned into silence by this news.

be met with
Her question was met with an uneasy silence.

observe (= as a sign of respect for the dead, etc.)
A minute's silence for the victims will be observed.

fill
She filled the silence with music.

come over sth, descend, fall, fall over sth, settle, settle over sth
A sudden silence fell over the room.

hang, prevail, reign
Silence reigned.

linger
A heavy silence lingered in the air.

envelop sth, fill sth
Silence filled the room.

ensue, follow
deepen, grow, lengthen, spread, stretch
He thought for a moment, the silence lengthening.

greet sth
A stunned silence greeted her announcement.

in (the) silence
They ate their breakfast in silence.

two minutes' silence, three minutes' silence (esp. BrE)
They observed two minutes' silence to remember the war dead.
Countries throughout Europe held a three minutes' silence.

deafening
The government's only response has been a deafening silence.

dignified (esp. BrE)
deliberate

keep, maintain
He has so far kept a dignified silence on the subject.

take as
I took her silence as a no.

surround
a debate to break the silence surrounding domestic violence

silence from
There seems to have been a deliberate silence from the newspapers.

a conspiracy of silence, a wall of silence
There is a conspiracy of silence about what is happening (= nobody is willing to talk about it).

a vow of silence
She has broken her vow of silence on the issue.