This is directly from Wikipedia and you can soak up more at these links:
graffiti (singular: graffito) - is writing or drawings that have been scribbled, scratched, or sprayed illicitly on a wall or other surface in a public place.
black book - a graffiti artist's sketchbook.
tag (scribble) - a stylized signature, normally done in one color. The simplest and most prevalent type of graffiti, a tag is often done in a color that contrasts sharply with its background. Tag can also be used as a verb meaning "to sign".
throw-up - a throw-up or "throwie" sits between a tag and a bomb in terms of complexity and time investment. It generally consists of a one color outline and one layer of fill-color. Easy-to-paint bubble shapes often form the letters.
one-liner - a tag, throwie, or bomb written in one constant motion.
straight letter - also referred to as "straights", "blockbusters" and sometimes "simples" are a direct, blocky, more readable and simpler style of graffiti.
wildstyle - graffiti with text so stylized as to be difficult to read, often with interlocking, three-dimensional type.
hollows - also referred to as "outlines" and "shells". A hollow is a piece of graffiti that contains no fill.
backjump - a quickly executed throw up or panel piece.
bomb - to bomb or hit is to paint many surfaces in an area.
heaven spots (or shorter as heavens) - pieces that are painted in hard-to-reach places such as rooftops and freeway signs, thus making them hard to remove.
paint-eater - an unprimed surface such as raw wood or concrete that eats up standard spray paint.
crew - a crew, krew, or cru is a group of associated writers or graffiti artists that often work together.
writer - a practitioner of writing, a graffiti artist.
head - similar to a king or queen, a "head" is a writer who has much skill and a high reputation among other writers in his area.
knight - a respected writer whose skills are still progressing.
rook - trusted member of a crew.
angels - famous or respected writer who have passed away.
up - writers become up when their work becomes widespread and well-known.
soak up - to consider other pieces for inspiration.
So with that under our belts, I have a little extra inspiration for you to soak up. :D
