adj

• (archaic, also figuratively) Full of nits.
  "About mid-night do I walke, and for the trickes I play they call me Pach. When I find a slut asleepe, I smuch her face if it be cleane; but if it be durty, I wash it in the next pisse-pot that I can finde: the balls I use to wash such sluts withal is a sows pancake or a pilgrimes salve. Those that I find with their heads nitty and scabby, for want of combing, I am their barbers, and cut their hayre as close as an apes tayle; or else clap so much pitch on it, that they must cut it off themselves to their great shame."
• (chiefly British, slang) Foolish, inane.
  "Stephen Colbert went overtime to get into the “nitty crazy” of President Donald Trump’s press conference with Russian President Vladimir Putin on Monday, noting that, he was shaken to his core, but “at 54, there’s not a lot of core left.”"

noun

• (African-American Vernacular, MLE, slang) A dope fiend, a druggie.
  "See me breeze in a cream Bentley / Fronting in the sun that’s two-seated / Believe it, pull up to the light and now you looking defeated / Girl, grilling my ice got you heated (yeah) / Yep, beef with the nitty I never needed (wha-wha)"

adj

• (Excessively) detailed or specific; fastidious, fussy, nit-picky.
  "Clearly, it’s that Secretariat is overrated. OK, exhale. I’m not trolling you. I’m just being extremely nitty about the marginal shades of “really, really great.” By “overrated,” I certainly don’t mean to imply that Secretariat isn’t the best 3-year-old American racehorse in history – he is."
• (poker slang) Of a poker player: playing in an overly cautious and reactive manner.
  "Over the past year and a half Isildur1 has captivated the poker community with his overly aggressive play and mesmerizing swings in the highest cash games online. His most intriguing characteristic isn’t his combativeness or his disregard for money; however, it’s his anonymity. […] [Phil] Hellmuth is far too nitty to be the face behind an online maniac such as Isildur1, he’s already rumored to be "#1_Lucky_One" and he’s clearly not spending copious amounts of time grinding high stakes in Sweden."

adj

• (obsolete, rare) Shining; elegant, spruce.
  "O dapper, rare, complete, sweet nitty youth! / Jesu Maria! How his clothes appear / Cross'd and recross'd with lace, sure for some fear / Lest that some spirit with a tippet mace / Should with a ghastly show affright his face."