/ bʌlb; NAmE / noun
1.
(also ˈlight bulb ) the glass part that fits into an electric lamp, etc. to give light when it is switched on :
a 60-watt bulb
a room lit by bare bulbs (= with no decorative cover)
2.
the round underground part of some plants, shaped like an onion, that grows into a new plant every year
3.
an object shaped like a bulb, for example the end of a thermometer
••
WORD ORIGIN
late Middle English : via Latin from Greek bolbos onion, bulbous root.