IPA: //ˈteɪstləsnəs//
KK: /ˈteɪstləsnəs/
The quality or state of lacking flavor or interest.
The dish was criticized for its tastelessness, as it had no distinct flavors.
Tastelessness → It is formed from "taste" (from Old French *taster*, meaning to perceive flavor) and "-less" (meaning without) and "-ness" (meaning a state or quality). The word "tastelessness" refers to the state of being without taste or flavor.
Think of being 'without' ('-less') the ability to 'perceive flavor' ('taste') — that's why tastelessness means lacking flavor.