Prog encompasses various styles dating back to the late 60s depending on influences and established music forms being blended together. Classical blended with rock is a style of prog called 'symphonic'. Jazz musicians that composed rock suites are called 'fusion' in the U.S.. In the U.K. jazz and rock combine in the style called 'canterbury'. In France it's called 'zuehl'. Freakout, jam style bands in Germany are called 'krautrock'; elsewhere they are called 'spacerock' and 'jambands'. Bands whos sound is dominated by synthesizers as both rhythm and lead instruments are called 'electronic'. There are many progressive style rock artists who are unclassifiable, who pushed the boundaries of rock in the late 60s and early 70s in completely unique ways such as Funkadelic, Frank Zappa and the early Santana band.
Prog is a nebulous term applied to artists who play rock instrumentation without regard to commercial, pop radio format restraints of song length and/or improvisational content.
Some examples of 70s prog artists beside those already mentioned are Emerson, Lake and Palmer, Mahavishnu Orchestra, Soft Machine, Magma, Embryo, Osibisa, Gong and Tangerine Dream.
Some examples of prog in the new millenium are The Flower Kings, Kenso, Ozric Tentacles, Groove Collective, Deus Ex Machina and Radio Massacre International.
2. My also refer to the manner in which one is dressed: One will usually sport a white button-down shirt and tight-fit pants (black jeans, leather, blue jeans, white pants).
"Did you see John Paul at the party yesterday? He was proggin' it up with his clean-ass white Calvin Klein button-down. He dressed mad prog."