IPA: /ˈbɪtə(r)ər/
KK: /ˈbɪtərər/
Having a sharp, unpleasant taste or smell that is often associated with something that is not sweet; more intense in this quality than something that is simply bitter.
The coffee was even bitterer than I expected, making it hard to enjoy.
Comparative: bitter
Superlative: bitterest
Bitterer → The word 'bitterer' is formed from 'bitter' (from Old English 'biter', meaning having a sharp taste or smell) and the comparative suffix '-er' (meaning more). The word 'bitterer' means more bitter than something else.
Think of 'bitter' as having a sharp taste, and when you add '-er', it means something is even more sharp or unpleasant in taste.