Incorrect spelling, explanation: this form, reversable is an incorrect one, although it may seem right, due to the fact, that if we take the suffix, the full-form word remains (in such cases we usually add suffix -able). However, in this case, we deal with the Latin word reverse, and with such words, we use the suffix -ible (reversible). Therefore reversible is the correct form.

Correct spelling, explanation: there is a general rule saying that complete root words use suffix -able, but in this case, we focus on the fact, that reverse is of Latin origin, so it uses the suffix -ible. Therefore reversible is the correct form, and not reversable. This word can be tricky, but we should remember to use -ible with Latin words, as in reversible.

Definition of reversible:
adjective, something that can be changed back to the way it was before; also: that has two sides as in clothing
The reaction is reversible, so pictures can fade in time.
I hope this problem is reversible and temporary.