IPA: /ˈsɪkliər/
KK: /ˈsɪkliər/
More sickly than something else; having a greater degree of illness or weakness.
After the flu, she felt sicklier than before and needed more time to recover.
Comparative: sicklier
Superlative: sickliest
Sicklier → It is formed from "sick" (from Old English *sēoc*, meaning ill or unwell) and the comparative suffix "-lier" (meaning more). The word "sicklier" means more ill or unwell than something else.
Think of someone who is 'ill' ('sick') and then imagine them being 'more' ill, which is what 'sicklier' means.