The "M..." in your query likely refers to common shorthand used in LGBTQ+ apps and forums:

"Male for Male," used to indicate interest in a male partner.

If you are looking for a specific video or scene, the title you provided is likely a direct copy of a file name or a search string from an adult media database. Searching these specific names on industry-specific platforms will yield more direct results than a general web search.

In contemporary slang, a " guncle " is a gay uncle who often takes on a supportive, mentoring, or "cool elder" role for younger family members or queer youth.