1. 
[syn: ailing, indisposed, peaked(p), poorly(p), sickly, unwell, under the weather, seedy]
The Collaborative International Dictionary of English v.0.48:
Ail \Ail\ ([=a]l), v. t. [imp. & p. p. Ailed ([=a]ld); 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. [root]3.]
   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.
   [1913 Webster]
         What aileth thee, Hagar?                 --Gen. xxi.
                                                  17.
   [1913 Webster]
   Note: It is never used to express a specific disease. We do
         not say, a fever ails him; but, something ails him.
         [1913 Webster]
The Collaborative International Dictionary of English v.0.48:
ailing \ailing\ adj.
   sick; unhealthy. Opposite of well or healthy.
   Syn: indisposed, peaked(predicate), poorly(predicate),
        sickly, unwell.
        [WordNet 1.5]
WordNet (r) 3.0 (2006):
ailing
    adj 1: somewhat ill or prone to illness; "my poor ailing
           grandmother"; "feeling a bit indisposed today"; "you look
           a little peaked"; "feeling poorly"; "a sickly child"; "is
           unwell and can't come to work" [syn: ailing,
           indisposed, peaked(p), poorly(p), sickly,
           unwell, under the weather, seedy]