What does this idiom mean: 'out of your mind'? Does it mean 'unsure'?

[nona m.]

English Idioms and Expressions, Elementary Level

ESL/EFL Test #6 "Out of Control", question 2

If you think I'm going to parachute out of a plane for fun, you must be out of your mind.

(a) mad
(b) unsure
(c) unusual
(d) uncertain

English Idioms and Expressions, Elementary Level

ESL/EFL Test #6 "Out of Control", answer 2

If you think I'm going to parachute out of a plane for fun, you must be mad.

Correct answer: (a) mad
_________________________

what is unsure?

nona m.

[Conchita]

Dictionaries are very helpful and even necessary when learning a language.

This one, for example, is appropriate for learners, as it gives clear and simple definitions:

http://dictionary.cambridge.org/define.asp?key=87106&dict=CALD