What does "cramp one's style" mean?
Solution 1:
Dude — you're cramping my style!
means that "Dude" is behaving in such a way as to inhibit whatever behavior the speaker is engaging in at the moment — whether that be trying to have a conversation, playing a game, trying to get romantic with a woman, whatever. Say I was in a bar chatting up some hottie and you walked over and started trying to sell me insurance, I might tell you you were cramping my style.
Solution 2:
I think this could apply to any intrusive behaviour by another that hinders my natural and usual way of doing things, my lifestyle, the plans I had that I can no longer execute easily.
Solution 3:
Although this question borders on general reference, it is perhaps worth noting that the cramp of "Dude, you're cramping my style" is not particularly closely related to the cramp of (for example) "his shoulder cramped while he was sitting in the dugout during the seventh inning." At any rate, that seems to be the view of the American Heritage Dictionary of the English Language, fifth edition (2010), which covers the meanings of cramp1 and cramp2 as separate entries:
cramp1 n. 1. An involuntary, spasmodic muscle contraction causing severe pain. 2. A temporary partial paralysis of habitually or excessively used muscles. ... v. cramped, cramping, cramps tr. To affect with as if with a cramp. —intr. To suffer from or experience cramps. {Middle English crampe < Old French, of Germanic origin.}
cramp2 1. a frame with an adjustable part to hold pieces together; a clamp. 2. A cramp iron. 3. A compressing or restraining force, influence, or thing. 4. A confined position or part. tr.v. cramped, cramping, cramps 1. To hold together with a cramp. 2. To shut in so closely as to at to restrict the physical freedom of: [example omitted]. ... —idiom: cramp (one's) style To restrict or prevent from free action or expresion. {Middle English crampe, probably < Middle Dutch, hook, cramp, Adj., probably akin to Icelandic krappr, contrained, tight, and Old High German cranf, squeezed.}
So "you're cramping my style" doesn't mean to suggest "you're causing my style to suffer involuntary spasms or contractions" but rather "you're causing my style to be restricted, confined, or limited."
Christine Ammer, The American Heritage Dictionary of Idioms, second edition (2013) asserts that the idiomatic use of "cramp [one's] style" is not much more than 100 years old:
cramp someone's style Restrict or prevent someone from free action or expression, as in It really cramps my style when Mom hovers around me while I'm making dinner. Although in 1819 Charles Lamb complained that using different inks cramped his style of writing, the present sense of this colloquial term dates only from the early 1900s.
The earliest match I could find for this idiom in the Elephind newspaper database, however, comes from "Objectors to Ready-Made Clothing," an advertisement for Gusky's Department Store, in the Pittsburgh [Pennsylvania] Dispatch (April 21, 1889)—and coincidentally, it involves use of the word dude, as well:
The Dude: Afraid They Would Cramp His Style, Spoil His Shape and Destroy His Individuality.
The expression also pops up in Australia at a fairly early date. From W.J. Ford, "Cricket 'Specials': Famous Present Day Cricketers," in the [Adelaide, South Australia] Chronicle (December 28, 1901):
Every one likes Ranjy. There was a notion in the air when he first began to startle the world that very big scores were not for him, as be did not possess the necessary stamina. Those ideas have vanished into thin air, for Ranjy is as good a stayer as anyone, and what is more, he can maintain his superiority over most men on bad wickets as well as good. His only trouble is cold, which naturally cramps his style and spoils his pleasure; indeed, his favorite silk shirt seems but a sorry defence against the Arctic weather with which we are often blessed in May, and even in June.