Glossary

Glossary - or terminology:

Actor
AI
Alpha Channel
Attribute
Bot
Bot Pathing
Brush
BSP - binary space partitioning is the method for representing 3d space geometry, in mapping often used as a synnonym for brushes, brushwork or basic geometry
BSP Hole - error caused by misaligned brushes or simply by too complex brushwork
Builder Brush - red brush acting as a "cursor" when building brushes (BSP geometry)
Cascade
Kismet
Level (or map) - 3D area depicting some particular place with some layout and pickup placement
Map - see level
Material
Matinee
Static Mesh
Texture
[[[uu
Variable
Vertex
Viewport
Z-axis

Resources

Terminology on Unreal Wiki