Special case of Polysemous

Bisemous is fine, but let me argue for it.

First, consider that monosemy (and monosemous) is recognized by Oxford Dictionary as:

Linguistics

The property of having only one meaning.

Next, consider that polysemy (and polysemous) is also recognized by Oxford Dictionary as:

Linguistics

The coexistence of many possible meanings for a word or phrase.

While bisemous is not recognized by Oxford, it is easily formed and understood on analogy with monosemous and polysemous.

Wiktionary even has an entry on bisemous:

(linguistics)

Having two meanings or interpretations.

Now, some might object that bi- is Latin, not Greek like mono- and poly-. But I would argue that bi- is more easily understood as "two" than the Greek equivalent di-. Further, I personally have encountered bisemous more than disemous, although there are occurrences of the latter.

The fact that your spellchecker doesn't recognize it should not deter you from using it.