1 ailing, unsound, sick, indisposed, infirm, unhealthy, in a bad way, diseased, afflicted, in bad health, sickly, unwell, not well, out of commission; invalided, valetudinarian; Colloq under the weather, in a bad way, poorly, not up to snuff, out of sorts, on the sick-list, off one's feed, Slang Brit dicky, seedy:
Call a doctor - this man is ill. I was rather ill last night after eating that fish mousse
2 bad, wicked, sinful, evil, iniquitous, immoral, depraved, vicious, vile, wrong, corrupt:
Police raided several houses of ill repute.
3 hostile, unfriendly, antagonistic, belligerent, malevolent, malicious, ill-wishing, unkind(ly), harsh, cruel:
The reading of the bequests sparked ill will amongst the heirs.
4 harmful, hurtful, injurious, detrimental, damaging, pernicious, dangerous, adverse, deleterious, baleful, bad, unfavourable, destructive, disastrous, catastrophic, ruinous, cataclysmic:
He suffered no lasting ill effects from the accident.
5 bad, miserable, wretched, disastrous, unfavourable, unpropitious, untoward, disturbing, unfortunate, unlucky, inauspicious, ominous, unpromising, sinister, unwholesome:
Ill fortune led Ulysses to our isle. It is an ill wind that blows nobody good.
6 ill at ease. uncomfortable, discomfited, uneasy, edgy, on edge, fidgety, nervous, anxious, disturbed, distressed, troubled, awkward, unsure, uncertain:
I felt ill at ease in the presence of so august a personage.
7 evil, abuse:
Speak no ill of her in my home!
8 harm, damage, injury, hurt, mischief, trouble, misfortune, misery, affliction, pain, distress, woe, woefulness, discomfort, unpleasantness, disaster, catastrophe, cataclysm, calamity, adversity, damage, suffering, ruin, destruction:
You will be held responsible if any ill befalls the children.
9 injustice, inequity, wrong, evil, sin, transgression, abuse, mistreatment, maltreatment:
He entered politics hoping to cure some of society's ills.
10 badly, adversely, unfavourably, poorly, inauspiciously, unfortunately, unluckily:
Don't speak ill of the dead.
11 badly, adversely, unfavourably, critically, harshly, unkindly:
Please don't think ill of me for failing to attend your wedding.
12 unkindly, harshly, unfairly, unjustly, improperly, badly, wrongly, wrongfully, unsatisfactorily, poorly, malevolently, maliciously:
He insists that he was ill-treated when in prison.
13 scarcely, hardly, by no means, in no way:
It ill behoves you to criticize other people's English.