The Brief: BTW stands for "by the way."

Bluesquiggle
DEEP DIVE

BTW (also pronounced “B-T-Dubbs”) is short for “by the way.” It is primarily used as a transitional phrase to introduce a new topic of conversation. BTW can also be used to interject a humorous non sequitur or to nonchalantly call attention to something important or significant, usually in an ironic way.