Is 'irreasonable' as the opposite of reasonable acceptable or not? [closed]

Solution 1:

The term "irreasonable" is not acceptable to well-educated native English speakers.

As evidence:

1. it's not in the Oxford English Dictionary - which is the ultimate arbiter of "good English"; and
2. automated spell checks (for instance, in Microsoft Word and even in this text box on StackExchange) mark the spelling as incorrect.

The term "irreasonable" is clearly capable of being understood, and a quick Google search shows the term is occasionally used.

However, any person using the term would convey the impression that he or she is either a non-native speaker or a poorly-educated native speaker.