Gigadeathcrime

noun
A criminal act causing billions of deaths.
Source
Excession

Gimboid

noun informal
An incompetent person.
Origin
Possibly a pairing of ‘gimp’ and the suffix -oid (resembling).
Source
Red Dwarf

Girdlecity

noun proper
A city that encircles a planet.
Source
The Hydrogen Sonata

Girlygirl

noun
A professionally flirtatious hostess, akin to a geisha.
Source
The Ballad of Lost C’mell

Godshatter

noun
Fragments of a superintelligence melded with a human-level intellect.
Source
A Fire Upon the Deep

Gridfire

noun
A method of creating a dimensional rift that releases astronomical amounts of energy into realspace from the energy grid between universes.
Source
Consider Phlebas

Grislesque

adjective
Of a simulated scenario: so complex as to cause horror or disgust.
Origin
Corruption of ‘grisly’.
Source
The Hydrogen Sonata

Grok

verb
To understand so thoroughly that the observer becomes a part of the observed.
Source
Stranger in a Strange Land

Grosstopical

adjective
Crudely physical; not taking into account the topography of Cleavage.
Origin
Formed from gross (without deductions) and topical (related to a particular place).
Source
The City & The City

Headvid

noun
Video viewed by direct interface with the visual cortex of the brain.
Source
Voice of the Whirlwind

Hearthmate

noun
One’s fellow resident in a shared household.
Source
Coming of Age in Karhide

Hegemonarchy

noun
A form of government comprising a ruling class and a supreme leader.
Origin
Portmanteau of ‘hegemony’ and ‘monarchy’.
Source
Use of Weapons