Wiktionary
n. A kind of lamp typically used more for decoration than illumination, in which the gentle flow of randomly-shaped clumps of wax purportedly suggests the flowing of lava.
Wikipedia
A lava lamp (or Astro lamp) is a decorative novelty item, invented in 1963 by British accountant Edward Craven Walker, the founder of the British lighting company Mathmos. The lamp consists of a wad of a special coloured wax mixture inside a glass vessel the remainder of which contains clear or translucent liquid; the vessel is then placed on a box containing an incandescent light bulb whose heat causes temporary reductions in the density and viscosity of the wax. The warmed wax rises through the surrounding liquid, cools, loses its buoyancy, and falls back to the bottom of the vessel in a cycle that is visually suggestive of pāhoehoe lava, hence the name. The lamps are designed in a variety of styles and colours.
Usage examples of "lava lamp".
When she scanned back to the previous channel, the Technicolor Lava lamp was gone.
The city burst with colors, from the huge tapestries that adorned the sides of whole buildings, to the free-standing sculptures on each street corner, to the dazzling, floating light shows that seemed to appear and disappear in random locations-Carol commented that they looked like super-advanced lava lamps, then had to explain what a lava lamp was.
Somehow he couldn't imagine holding an effective interrogation with the suspect in a beanbag chair under a hot lava lamp.
But the shelves were filled with a host of other things: tennis rackets, hockey sticks, umbrellas, a spade, a notebook computer, a wooden leg, several mugs, dozens of shoes, pairs of binoculars, a small log, six glove puppets, a lava lamp, various CDs, records (LPs, 45s, and 78s), cassette tapes and eight-tracks, dice, toy cars, assorted pairs of dentures, watches, flashlights, four garden gnomes of assorted sizes (two fishing, one of them mooning, the last smoking a cigar), piles of newspapers, magazines, grimoires, three-legged stools, a box of cigars, a plastic nodding-head Alsatian, socks .
For a moment he stared intently at the swooping shadows, which were as amorphous as the molten forms in a Lava Lamp, but he could not make the connection.
There was a lava lamp atop the television, with a huge brass peace symbol attached to its base.