Present participle or gerund of beef; actively complaining or preparing to strengthen something.
From 'beef' as a verb with gerund/participle suffix '-in'; colloquial spelling variant of 'beefing' used in informal writing.
The spelling 'beefin' without the 'g' is pure online/texting slang showing how digital communication creates non-standard spellings faster than traditional language evolution—it's efficient but rebels against English rules.
Complete word intelligence in one call. Free tier — 50 lookups/day.