Glossary of Hang Gliding Terms

ASL
Above sea level
basetube
See "control frame."
boo-wah
You didn't expect to find that listed as a jargon word, did you? I've no idea of its origin, but it's pretty self explanatory. It means there's great flying conditions out there, and we're going high and far.
cloud suck
See "suck."
control frame
The triangular frame that the pilot uses to control the glider is called the "control frame." It consists of two "downtubes" connected by a "basetube." The tops of the downtubes are bolted onto the "keel."
cumies
Cumulus clouds.
downtube
See "control frame."
evening magic
Evening magic is when a valley that's been heating all day releases its hot air upwards, as cooler air from higher ground flows downwards. The resulting air is gently buoyant, and widespread areas of lift can support gliders until sunset and beyond.
fpm
Feet per minute.
GPS
Global Positioning System. The US government operates a number of satellites that send out signals, which, when read by a GPS receiver, allow the receiver to compute its whereabouts (in latitude and longitude) anywhere on our planet.
H1, H2, H3, H4, H5
These are proficiency ratings for hang-glider pilots. H1 (or Hang 1) is a beginner rating, H2 is called novice, H3 is intermediate, H4 is advanced, and H5 is master. Practically (though loosely) speaking, H1 doesn't allow you to do very much, H2 means you can take high flights under supervision, H3 means you can fly almost anywhere you'd want to, and H4 is required for a very few sites. H5 is pretty much a badge of honor, and can only be attained by pilots who have done lots and lots of flying from lots of places.
LZ
Landing zone.
MSL
Mean sea level. When we say 5000' MSL we mean 5000 feet above sea level. I know the abbreviation doesn't make any sense in the way we use it, but that's its colloquial use anyway.
S2F
See "speed to fly"
sink alarm
The sound made by the vario to warn the pilot that he's flying in strongly sinking air. The vario makes a different sound when the glider is rising. This sound is a much happier one for the pilot.
sled
...or "sled ride"...is when you launch your glider and find no lift, sinking all the way to the ground. The term is used by participants in all forms of gliding, whether hang gliding, paragliding, or sail-plane gliding.
slot
An area cleared of trees on a tree-covered mountain or ridge, allowing gliders to launch.
speed to fly
This is a complicated subject, but there is an optimum speed to fly for any combination of sinking/lifting air and wind speed/direction. "Optimum" here means furthest glide over the ground. A sophisticated flight computer, with information from a GPS, can compute the windspeed. The flight computer itself measures the lift or sink. Knowing the glider's performance characteristics, the computer can tell the pilot what speed he should fly at to maximize his glide. (This explanation gets very complex if we start to worry about maximizing speed over the ground, but I won't get into that.)
suck
Cloud suck is a phenomenon where pilots can get sucked into clouds as the lift increases strongly near the cloud. Extending the concept, pilots joke around and talk about "tree suck," "ground suck," and all kinds of variants on the "suck" theme to explain their misfortunes.
variable geometry
Higher-performing gliders have the capability for the pilot to change their geometry while in flight. The pilot pulls on a string to tighten the sail, and releases it to loosen the sail. A tight sail makes for a better glide, but makes the glider harder to control. Therefore, (roughly speaking) we use a loose VG setting while working thermals, and a tight VG setting while crossing areas of sink in search of the next thermal.
VG
See "variable geometry"
wuffo
A non-pilot. An ordinary person. The origin of the word is obscure, but it's thought to be a contraction of "what for." When non-pilots encounter pilots, they tend to ask a lot of questions: what for is this? what for is that? what for is the other?