1. [rare] The practice of translating hot spots from an HLL into hand-tuned assembler, as opposed to trying to coerce the compiler into generating better code. Both the term and the practice are becoming uncommon. See tune, by hand; syn. with v. cruft.
2. [common] More generally, manual construction or patching of data sets that would normally be generated by a translation utility and interpreted by another program, and aren't really designed to be read or modified by humans.