IPA: /ˌmɒnəˈmeɪnɪkli/
KK: /mɑnəˈmænɪkli/
In a way that shows excessive focus or obsession on a single idea or subject.
He pursued his project monomaniacally, ignoring all other responsibilities.
Monomaniacally → It is formed from "mono-" (meaning single or one) and "mania" (from Greek "mania", meaning madness or obsession) and the suffix "-ally" (meaning in a manner). The word describes acting in a manner that is obsessed with a single idea or subject.
Think of being obsessed with just one thing ('mono-') to remember that 'monomaniacally' means acting in a way that shows a single-minded obsession.