Synonyms for Sick:

adj.

diseased (adjective)
affected, infirm, nauseous, diseased, ill, ailing, infected, Inflicted, decrepit, unhealthy, morbid, handicapped, disabled, indisposed, sickly, cursed, pestilent.
fed up, displeased (adjective)
tired, weary, disgusted.
morbid, gross (adjective)
sickly.
not healthy, not feeling well (adjective)
frail, infirm, not so hot, sick as a dog, infected, under the weather, under medication, unwell, feverish, suffering, delicate, green, impaired, imperfect, peaked, bedridden, diseased, nauseated, indisposed, weak, feeble, in poor health, poorly, queasy, ailing, disordered, invalid, funny, declining, ill, incurable, in a bad way, rickety, confined, unhealthy, hospitalized.
palsied (adjective)
spastic.
queasy (adjective)
bilious.
revolting (adjective)
sickly.
rocky (adjective)
rickety.
sickly (adjective)
invalid.
unhealthy (adjective)
diseased.

adv.

sickly (adverb)
delicate.

n.

detestable, despicable, dreadful, repulsive, appalling, revolting, horrible, disgusting. hateful, health, inhuman, pitiless, uncharitable, cruel, evil, monstrous, unkind, hard, awful. anorexic, bed-blocker, asthmatic, agoraphobe, amnesiac, the critical list, depressive, case, anemic. bring up, tired, weary, come up, chuck up, cloy, bloated. ill (noun)
incurable, in a bad way, under medication, physically run down, in poor health, hospitalized, on the blink, frail, feeling poorly, feeble, suffering, dy, rabid, morbid, quarantined, Distempered, invalid, confined, rickety, impaired, out of kilter, not so hot, looking green about the gills, coming down with, imperfect, sick as a dog, disordered, declining, delicate, weak, broken-down, at a low ebb.
mentally ill (noun)
certifiable, deranged, diminished responsibility, confused, hysterical, bipolar.

Other synonyms:

weak, unfit, disordered, feeble, worse. confined, rabid, rickety, peaked, tired, fragile, anemic. failing, weary. unwholesome. faint
faint.
fragile
frail.