Let's describe the inscrutable... If your Thursday night's still blank, we've found a filler. Mos Def, arguably one of America's top slashers (music/movies/plays/protests), will be confabbing with Rolling Stone's Anthony DeCurtis at the 92nd St Y. As his past year alone has been a whirlwind of acting -(Be Kind Rewind), and activism -public appearances regarding the Jena 6 and Hurricane Katrina, this talk should be a doozy. Not to mention the irony of the setting. Old white men running this rap s**t indeed! (Lexington Ave. at 92nd St. 212-415-5500. Feb. 28 at 8.)