What does "gish" mean?

[VictorianMale]

I see here all the time, and I cannot puzzle it out...

[Darth Stabber]

FighterCasters. I don't know where the term originates, but the general Idea is that a fighter is better with magic so make your fighter also a caster, so he can buff himself (or add spell damage to melee attacks ala duskblade)

[Dusk Eclipse]

It is a term coined from 2ed planescape (I think), it refers to a workable combination of a warrior mage (mage being almost any magical class, being Wizard, sorcerer, psion, etc)

The standard against which they are measured is getting at least BAB +16 and 9th level spells.

Originally it refered to Githyanki Warrior/Wizards IIRC

[Endarire]

Gish (http://en.wiktionary.org/wiki/gish).

Practically, it means a martial/caster or martial/manifester character. Some classes are self-contained gishes, like PsyWars, Druids, Clerics, and some Ardents.

[RaginChangeling]

I see here all the time, and I cannot puzzle it out...

Someone who uses both spells and has some martial ability, probably a corruption of the Githyanki from earlier editions who were famed as monsters for doing just that.

[classy one]

In the Gith language, Gish means "skilled" as in a member of with fighter/wizard class levels. This is in addition to the considerable psionic like abilities that they have at their disposal, making them adept at combining martial, acrane and psionic into one awesome force.
The Githyanki really are the coolest.

In usual terms it refers to anyone who can "cast" things and fight.

Some people feel the need to narrow that term to "has BAB+16 and 9th level powers/spells" by level 20, while others have a broader definition.