Synonyms for Shush:

n.

MYOB, mind your own business, hold your tongue, that will do, shut it, can it, suck it up, button it, dry up, SH.

v.

silence (verb)
hush, silence, dry up, mute, shut up, lull, quiet, still, quieten.

Other synonyms:

quieten. quiet
can it.
quieten
quieten.
Other relevant words:
dry up, hush, MYOB, hold your tongue, stop, shut up, bar, SH, thwart, quieten, restrain, sounds, check, prevent.