Free Electron Laser

stands for ree lectron aser; a tunable laser made by wiggling a beam of electrons ( Jefferson Lab's FEL is the most powerful in the world.)

Frank Effect Level. A level of exposure or dose that produces irreversible, adverse effects at a statistically or biologically significant increase in frequency or severity between those exposed and those not exposed.

Flight Engineer Licence

lit. dark

Flexible Exchange Lease. Obsolete IBM lease offering which made it easy for customers to change to new IBM products as they emerged. Many FELs included Technology Conversion Option

The front-end loose page(s).

Front End load: the charge levied by sellers (distributors) of unit trusts

Fair Employment Law