Abbr. for.... since everyone loves math, how about, Lucas–Lehmer primality test for Mersenne numbers; or the Cholesky decomposition, an algorithm to decompose matrix A into a lower Matrix L. No? Medicine then, Laser lithotripsy, a surgical procedure to remove urinary stones. Linus Media Group? Oh, all right, I'll make something up. A junior commissioned officer who is in command of one side of a unit (not the right side)