From Halopedia, the Halo wiki
"Bumblebee" is the name applied to a series of escape pods operated by the UNSC Navy.
Bumblebees are types of lifeboats used by the UNSC to ferry personnel away from ships that are in danger of destruction. Individual Bumblebees are identified with three letters from the Phonetic alphabet and one or two numbers (eg. Lima Foxtrot Alpha 19, Whiskey Tango Foxtrot One).