adj. (sicklier, sickliest) 1 a of weak health; apt to be ill. b (of a person's complexion, look, etc.) languid, faint, or pale, suggesting sickness (a sickly smile). c (of light or colour) faint, pale, feeble. 2 causing ill health (a sickly climate). 3 (of a book etc.) sentimental or mawkish. 4 inducing or connected with nausea (a sickly taste). 5 (of a colour etc.) of an unpleasant shade inducing nausea (a sickly green). sickliness n.
[ ME, prob. after ON sjukligr (as SICK(1)) ]