Mixed media (1950s?, fine art, 35M hits): Describes a work that mixes two or more visual media, often restricted to the disciplines of painting and sculpture.

Intermedia (1960s, fine art, 25M hits): Describes a work that mixes any two or more artistic disciplines usually recognized as separate. Popularized by the Fluxus group. (Coined by Dick Higgins.)

Hypermedia (1960s, computer science, 20M hits): Describes an organized collection of media files that the user can move between at will. Wikipedia is a hypermedia system. (Coined by Ted Nelson.)

Multimedia (1.2B hits)
1. (1960s, fine art): Describes a work that mixes any two or more media; largely replaced in current usage by “intermedia.” (Possibly coined by Bob Goldstein.)

2. (1990s, computer science): Describes a device that can display multiple types of media–sound, video, text, images, etc.

3. (1990s, popular): Describes a work in any medium either created or experienced using such a device; largely replaced in current usage by “new media.”

New media (1990s, media theory, 69M hits): Describes works which are both created and experienced using a computer.

Transmedia (1990s, media theory, 3M hits): Describes a narrative dispersed across multiple works in multiple media, each of which contains only a portion of the complete story. A long-running franchise like “Star Wars” can be considered one epic transmedia work. (Coined by Marsha Kinder.)

Rich media (2000s?, design, 9M hits): Describes works distributed via the internet that make use of sound and video, as opposed to images and text.

(Hit counts from search performed 23 mar 12.)