Synonyms for Decease:

n.

check out, pass on to the Great Beyond, drop, kick in, bite the dust, cash in, kick off. death (noun)
death, dissolution, extinction, expiration, cessation, demise, ending, release, fatality, parting, quietus, annihilation, passing.
decease (noun)
die, go, death, exit, expire, perish, pass, pass away.

v.

die (verb)
fall, part, succumb, perish, pass, depart.
end (verb)
cease, end, cap, wrap up, stop, accomplish, finalize, pass away, terminate, exit, expire, halt, conclude, die, checkmate, pass on, finish, complete, close, culminate.
pass away; expire (verb)
depart, check out, go, pass, die, perish, cease, succumb, drop, pass away, pass on.

Other synonyms:

cease
pass.
die
pass away.
pass
cash in.

Usage examples for decease

  1. Susey, the little girl with the flower- ball, has had a loss too: the poor old man she lived with died within a few days of my dear uncle's decease – Kenelm Chillingly, Complete by Edward Bulwer-Lytton