without reason, sense or good judgement; silly

nonsensical, idiotic

that cannot be put into practice or used

unrealistic

not sensible because not doing well or achieving that which is intended

unrealistic

not being polite or caring about causing offence

without much thought

not advisable

not recommended

not expedient

futile

not having or showing good sense; not well-judged

imprudent

without the power to reason; absurd, not reasonable

illogical, senseless

(of behaviour) foolish and wrong (because of bad judgement)

ill-advised, deluded

foolish

silly, meaningless

not sensible; foolish

absurd, giddy, foolish

careless; indiscreet

thoughtless; unwary