Ail (#), v. t. [imp. & p. p. Ailed (#); p. pr. & vb. n. Ailing.] [OE. eilen, ailen, AS. eglan to trouble, pain; akin to Goth. us-agljan to distress, agls troublesome, irksome, aglo, aglitha, pain, and prob. to E. awe. .]

To affect with pain or uneasiness, either physical or mental; to trouble; to be the matter with; -- used to express some uneasiness or affection, whose cause is unknown; as, what ails the man? I know not what ails him.

What aileth thee, Hagar? Gen. xxi. 17.

⇒ It is never used to express a specific disease. We do not say, a fever ails him; but, something ails him.

© Webster 1913.

Ail, v. i.

To be affected with pain or uneasiness of any sort; to be ill or indisposed or in trouble.

When he ails ever so little . . . he is so peevish. Richardson.

© Webster 1913.

Ail, n.

Indisposition or morbid affection.

Pope.

© Webster 1913.