jargon.artrocity.com
New Hacker's Dictionary the Jargon File v 4.4.6
Of programs, very clever and efficient. A tense piece of code often got that way because it was highly tuned, but sometimes it was just based on a great idea. A comment in a clever routine by Mike Kazar, once a grad-student hacker at CMU: “This routine is so tense it will bring tears to your eyes.” A tense programmer is one who produces tense code.