venomous Asiatic and African elapid snakes that can expand the skin of the neck into a hood
"The cobra raised its head to reveal the distinctive hood it expands by spreading the loose skin around its neck."
Any of various venomous snakes of the family Elapidae.
"The cobra was among the most dangerous venomous snakes of the family Elapidae found in that region."
In plain English: A cobra is a type of venomous snake that can spread its neck hood to look bigger when it feels threatened.
"The cobra slithered out from under the rock and raised its hood at us."
Usage: Use "cobra" to refer to any highly venomous snake that can expand its neck ribs to form a hood when threatened, such as the king cobra or Indian cobra. Avoid using it for non-venomous snakes or other reptiles.
Initialism of Cabinet Office Briefing Room A.
"The media referred to the press gathering as a Cobra meeting, using the term as an initialism for Cabinet Office Briefing Room A."
The word entered English via Portuguese as cobra, which was originally borrowed from the Latin term colubra meaning a female snake. Over time, it came to refer generally to any of several venomous snakes with expandable hoods rather than just females.