fool·ish 
(flĭsh)
(flĭsh)adj.
1. Lacking or exhibiting a lack of good sense or judgment; silly: a foolish boy; a foolish purchase.
2. Capable of arousing laughter; absurd or ridiculous: a foolish grin.
3. Embarrassed; abashed: I feel foolish telling you this.
4. Insignificant; trivial: foolish little knickknacks.
foolish·ly adv.
foolish·ness n.
Synonyms: foolish, absurd, fatuous, ludicrous, preposterous, ridiculous, silly
These adjectives are applied to people or things that show an absence of good judgment or common sense: a foolish expenditure of energy; an absurd idea that is bound to fail; fatuous optimism that does not take the real problem into account; dismissed her ludicrous criticism; a preposterous excuse that no one believed; offered a ridiculous explanation for his tardiness; a silly argument.
These adjectives are applied to people or things that show an absence of good judgment or common sense: a foolish expenditure of energy; an absurd idea that is bound to fail; fatuous optimism that does not take the real problem into account; dismissed her ludicrous criticism; a preposterous excuse that no one believed; offered a ridiculous explanation for his tardiness; a silly argument.