What is the meaning of Unibody?

An automobile construction technique in which the body is integrated into a single unit with the chassis rather than having a separate body-on-frame.

A body of this type.

A shell that is the principal source of structural strength of an object; also, its design and construction.

A style of mobile phone, tablet, or laptop computer where the user cannot replace the battery because the device is manufactured as a single sealed unit.

Source: wiktionary.org