Letter-Hyphen-Word Words

I was surprised at how common words of the form "X-foo" are. I can come up with at least one for every letter. (I do think the "P-", "S-", "M-", and "N-" ones are a bit obscure.) Most of these are specifically American terms.

If you can think of more, please let me know!

A-list
The group of people who are the most desirable for something.
A-levels
A set of exams given at about age 18 (British).
B-school
(Graduate-level) Business School
C-rations
World War 2-era military term for canned rations
C-note
Century note, i.e. $100 bill (somewhat passé term)
D-day
This is military parlance for "the day of the invasion". "D" is a variable that allows planners to talk about the schedule of operations without actually knowing which day is going to be the invasion day. (This is important because the actual invasion day usually isn't determined until the last minute.) So, for example, two days before the invasion is "D minus 2"; three days later is "D plus 3". The "D" just stands for "day". (The hour of the invasion is "H-hour", with "H" standing for "hour".) "D-Day" has come to be popularly known as the day that the Allied troops invaded Normandy -- one of the pivotal battles of World War 2.
E-mail
Electronic mail
F-word
A common euphemism for a common swear word
F-4
A World War 2-era term designating someone who the military rejected as unfit for duty.
G-string
A very small garment that perhaps does, perhaps does not, cover the genitals. (Probably named after the thickest string on a violin.)
H-bomb
Hydrogen bomb
I-beam
Metal beam with a cross-section in the shape of a capital (serifed) "I".
J-school
Journalism school. (The phrase is not terribly commonly used except by journalists.)
K-9
Police dog ("ca-nine"). (Mostly used by police departments.)
K-12
Schools teaching from ages five ("Kindergarten") to age 18 ("grade 12").
K-car
A family of cars sold by Plymouth in the mid 1980s.
K-mart
Brand name of wide-spread discount department store.
L-bracket
Metal bracket with a cross-section that looks like a capital "L".
M-dash
(Usually spelled "emdash".) Term for a long dash, with width equal to that of a lowercase "m".
N-dash
(Usually spelled "endash".) Term for a short dash, with width equal to that of a lowercase "n".
N-Channel
A particular type of transistor.
N-word
A common euphemism for a common swear word
O-Ring
O-rings are gaskets that have a cross-section that looks like an "O".
O-levels
A set of exams given at about age 18 (British).
P-Funk
A particular rock band.
P-Furs
Short for Psychadelic Furs, another rock band.
P-Channel
A particular type of transistor.
Q-tips
Cotton swabs on sticks; most commonly used for cleaning ears.
R-value
Quality rating for building insulation.
S-set (tset?)
Letter in the German alphabet (ß).
T-shirt
Collarless short-sleeved knit shirt having roughly the shape of a capital "T".
T-ball
Form of baseball where, instead of a pitcher, balls are set on a tee.
T-square
Drafting tool that has roughly the shape of a capital "T".
U-boat
Underseas boat, i.e. submarine. World War 2 military term borrowed from German.
U-joint
Universal joint -- commonly found in automobile transmissions
V-neck
A type of shirt with a neckline in the shape of a capital "V". Usually refers to sweaters.
V-day
Victory day. World War 2 military term, usually used with another letter to designate which theater of war: VE-day for Europe and VJ-day for Japan.
W-2
A U.S. tax form given by employers to their employees and the government, detailing how much income and taxes the employee received/paid in the previous year. (Thanks to Kurt Miller!)
X-ray
A piece of the electromagnetic spectrum that can penetrate many solid objects; also equipment that uses that technology or images made with such equipment.
X-chromosome
One of two variants of the sex-linked chromosomes, shaped like a capital "X".
Y-chromosome
One of two variants of the sex-linked chromosomes, shaped like a capital "Y".
Z-Buffering
An computer graphics algorithm used to figure out which objects are visible and which are hidden behind other objects. (Thanks to Ashe Taylor!)

Kaitlin Duck Sherwood
Updated 19 March 2001 to include "W-2".
Updated 17 September 2000 to update "D-Day".
Thanks to "tales" for explaining D-Day to me.