1 to attempt vainly

2 a vain attempt

3 delusion

1 to try in vain

2 futile attempt

1 wild fantasy

2 unwarranted thought

1 delusional disorder

2 (fig.) paranoia

1 to take rash action

1 to alter a text indiscriminately (idiom)

2 to make irresponsible criticism

1 a forced analogy (idiom); to jump to an unwarranted conclusion

1 ridiculous self-importance (idiom); arrogance

1 to be unduly humble (idiom)

2 to undervalue oneself

1 unwarranted talk the listener can take or leave (idiom); sth not to be taken too seriously