1 a sickly person or animal is weak, unhealthy, and often ill :
She looked pale and sickly.
She looked pale and sickly.2 especially British English a sickly smell, taste etc is unpleasant and makes you feel sick :
3 a sickly colour or light is unpleasantly pale or weak :
The walls were painted a sickly green.
a pale, sickly moon
The walls were painted a sickly green.
a pale, sickly moon