Synonyms for Ill:

adj.

•ailing (adjective)
sickly, sick.
•all (adjective)
sick.
•bad (adjective)
unfavorable, injurious, unkind, wicked, noxious.
•baneful (adjective)
poisonous, calamitous, baneful, evil, cursed, contagious, cancerous, infectious.
•bedridden (adjective)
laid up, disabled.
•diseased (adjective)
disabled, sick, affected, infected, sickly, infirm, decrepit, ailing, nauseous, unhealthy, cursed, indisposed, Inflicted, diseased, pestilent, handicapped.
•ill (adjective)
indisposed, infirm, hostile, peaked, unpropitious, woozy, inauspicious, ailing, afflicted, poorly, injurious, harmful, unfavorable, wicked, noxious, diseased, down, ruinous, ominous, deleterious, unhealthy, unwell, laid low, detrimental, queasy, under the weather, hurtful, unkind.

adv.

•all (adverb)
poorly, badly.

n.

low-grade, second-rate, pitiful, terrible, disgraceful, embarrassing. ruinous, hazardous, wicked, unsafe, risky, perilous, disastrous. disturbance, hurt, disturb, be unfavorable to, trials and tribulations, difficulty, nuisance, issue, baggage, burden, problem. •bane (noun)
curse, infection, plague, bane, doom, contagion, misfortune, poison, affliction, scourge, calamity, cancer, evil.
•catastrophe (noun)
havoc, calamity, misfortune, scourge, devastation.
•complaint (noun)
upset.
•condition (noun)
problem.

Other synonyms:

fragile, mischievous, injurious, unfavorable, deleterious, detrimental. hurtful, failing. terrible. down. •faint
faint.

Usage examples for ill

1. " Shouldn't eat it; it always makes you ill – Adventures of Bindle by Herbert George Jenkins

2. She looked cold and ill – The Card, A Story Of Adventure In The Five Towns by Arnold Bennett

3. " Do not take it ill said she, " I did it in a dream." – Household Tales by Brothers Grimm by Grimm Brothers