verb
-ens; -ened; -ening
somewhat formal :to become sick or to cause (someone) to become sick [no obj]
[+ obj] :to cause (someone) to feel disgusted or angry
be sickening for
Brit informal :to be starting to have or suffer from (an illness)
sicken of
[phrasal verb]
sicken of (something) US :to lose interest in (something) because you have had too much of it