idiotic
adj. B2 Upper Intermediate US //ˌɪdiˈɑtɪk// UK //ˌɪdɪˈɒtɪk// id·i·ot·ic
adj. extremely stupid or showing a complete lack of good sense. You use it to describe an action or idea that seems very foolish.
adj. characterised by extreme folly or a significant lack of intelligence. Often used to describe decisions, behaviours, or ideas rather than people's inherent mental capacity.
It was an idiotic mistake to leave the car unlocked.
The company lost thousands of dollars because of an idiotic clerical error that nobody noticed for weeks.
While the plan seemed idiotic to the seasoned engineers, the marketing team insisted that its very absurdity would capture the public's imagination.
From idiot + -ic.
Usage
Commonly used both attributively before a noun and predicatively after linking verbs like 'be', 'seem', or 'look'.