出典:Wiktionary
mucousy (comparative more mucousy, superlative most mucousy)
Although the noun mucus traditionally takes the adjective mucous as its counterpart (with suffix -ous), the fact that this pair is homophonous occasionally influences speakers to add another adjectival suffix (-y) for easy clarity in speech. Such redundancy for easy clarity is not rare (nor always incorrect) in natural language. The noun + -y counterpart also exists (mucusy); the same is true for callousy and callusy.