noun

• (now rare) A headband; a ribbon or other band used to tie the hair up, or keep a headdress in place, or for decoration.
  "In secret shadow, farre from all mens sight: From her faire head her fillet she undight, And laid her stole aside."
• (construction) A heavy bead of waterproofing compound or sealant material generally installed at the point where vertical and horizontal surfaces meet.
• (engineering, drafting, CAD) A rounded relief or cut at an edge, especially an inside edge, added for a finished appearance and to break sharp edges.
• (UK) A premium cut of meat, especially beef, taken from below the lower back of the animal, considered to be lean and tender; also called tenderloin.
  "fillet steak"

verb

• (transitive) To slice, bone or make into fillets.
• (transitive) To apply, create, or specify a rounded or filled corner to.