Real Dictionary

buffer
A buffer is something that prevents something else from being harmed or that prevents two things from harming each other.
The buffers on a train or at the end of a railway line are two metal discs on springs that reduce the shock when a train hits them.
verb: If something is buffered, it is protected from harm.

buffer in American English 1
a device using padding, springs, hydraulic pressure, etc. to lessen or absorb the shock of collision or impact
to protect against shock or impact; cushion or insulate
noun: an apparatus at the end of a railroad car, railroad track, etc., for absorbing shock during coupling, collisions, etc.
transitive verb: to treat with a buffer

buffer in American English 2
a person who buffs or polishes
noun: a device for polishing or buffing, as a buff stick or buff wheel

buffer in American English 3
an elderly man variously regarded as old fashioned, stodgy, ineffectual, etc.
noun: a foolish or incompetent person

buffer in British English 1
noun: one of a pair of spring-loaded steel pads attached at both ends of railway vehicles and at the end of a railway track to reduce shock due to contact

buffer in British English 2
noun: any device used to shine, polish, etc; buff

buffer in British English 3
noun: a stupid or bumbling man (esp in the phrase old buffer)