Real Dictionary

brittle
adjective: An object or substance that is brittle is hard but easily broken.
adjective: If you describe a situation, relationship, or someone's mood as brittle, you mean that it is unstable, and may easily change.

brittle in American English
easily broken or shattered because hard and inflexible
adjective: having hardness and rigidity but little tensile strength; breaking readily with a comparatively smooth fracture, as glass
intransitive verb: to be or become brittle; crumble
noun: a confection of melted sugar, usually with nuts, brittle when cooled

brittle in British English
adjective: easily cracked, snapped, or broken; fragile
noun: a crunchy sweet made with treacle and nuts

brittle in Mechanical Engineering
adjective: A brittle material breaks or splits easily.