from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A program, such as a spell checker or calendar, that remains loaded in memory so that it may be quickly recalled while another program is running, as found in operating systems which do not allow multitasking.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- Terminate and Stay Resident — a type of DOS program that can be run all time time, once it is loaded first, even when other programs are running.
t(erminate and) s(tay) r(esident).(American Heritage® Dictionary of the English Language, Fourth Edition)