Tasteless means having no flavour at all. Tasteless water, a tasteless meal, bland and tasteless.
Of food it is the strongest complaint short of unpleasant — a tasteless dish has failed at the only thing it was for. The other sense is about judgement: a tasteless joke offends by being crude, which is a different kind of taste entirely. Note that -less means without, in both senses.
1adjectivetastelessHaving no flavour at all.
“The hospital soup was watery and completely tasteless.”
2adjectiveoffensivelyOffensively crude.
“His tasteless joke about the accident upset everyone at the table.”
tasteless is a quality of lacking flavour.
Proto-Indo-European
*teh₂g-
la-cla
taxo — to touch sharply
Vulgar Latin
*tastāre — to touch or feel
Old French
taster — to taste, touch or hit
Middle English
tasten
English
taste
English, today
tasteless
Built from
From taste + -less. taste The verb is from Middle English tasten, borrowed from Old French taster (“to taste, touch or hit”), from unattested Vulgar Latin tastāre (“to touch or feel”), from taxitāre, an innovated form of la-cla taxo (“to touch sharply”), from tango (“to touch, to grasp”), ultimately from Proto-Indo-European teh₂g-, which is assumed to have had the same meaning as tangere. The noun came from the verb, and the two conflated after English lost its infinitive suffix -en, though tasten was most likely already used nominatively (as a), similar to Modern English tasting. Almost fully native smack, from smac,smak,smacke, from smæc,smæċċ.
Etymology from Wiktionary, CC BY-SA