A "legend" in my book is a broad term to describe a prominant figure in a business. He or she may not be considered an all time great, but has done enough to gain plenty of recognition for his line of work be it on the mike or in the ring or both. A legend has respect of peers and fans alike, and has been in the business for a good amount of time with impact.
An good example to me of a "legend" is Scott Hall/Razor Ramon. Not many put Scott in the Flair/Misawa/HBK/Hart/Kobashi/Steamboat/Benoit category of workers, but he is recognized as a good one who has earned respect for his technical ability from peers. He may not have a all time match, but his WM 10 ladder match with HBK was precedent setting, and certainly legendary and a good one that put HBK in a new status. Hall may not have the promo consistancy of a Jericho or Graham or Steve Austin, but Hall's segment work and overall work with the outsider angle/NWO is certaintly legendary and got super over. Hall was a perfect compliment to Hogan and big Kevin Nash in the original trio of the NWO where Hall played a perfect Havlicek to Cousy (Nash though not in size but in second in prominance) and Russell (Hogan) Due to his major role in the NWO (the biggest storyline in recent wrestling history arguably) and work as Razor Ramon, Hall is definately seen as a legend, but didn't quite have the body of work or the role as THE guy to be considered an "Icon", which leads to my next paragraph.
An Icon changed the business forever, is widely reguarded by all as an all time great, has a huge body of work be it in countless great matches, promos, segments, or a combination. An Icon is one who you KEEP the tv on whenever he is out and is either a man you love to hate as a heel, love as a face, or love to watch in the ring. An icon to me has shown he can be the prosperous batman of a company and can elevate performers to new heights when applicable. Icons are versatile as all time great singles stars and great tag team/stable wrestlers. These elite men to me have successful longevity hopefuly in both successful stints as heel and face, and have proven to draw money and ratings. The Icons must have both good to great mike work and excellent ring work (or vise versa). Icons have cross over success in multiple companies to prove they aren't one trick ponies or the product of a marketing machine (except for guys like Taker, who I certainly consider an Icon though he has only found success in WWF/E)
A list of some american Icons to me are guys like Georgeous George, Thez, Buddy Rodgers, the Original Sheik, Race, Terry Funk, Flair, Steamboat, (hey, maybe not great promo work, but his character personification in matches, all time body of work in America, ability to elevate good wrestlers to great are nearly unmatched. longevity and success in multiple companies with title runs certaintly helps as well as being in the greatest trilogy in American wrestling history vs Flar in 89 and being in 1 of the most influential matches in American wrestling history at wm 3 vs Savage), Andre the Giant, Piper and Hogan. More recent icons in the US to me include Bret Hart, HBK, Taker, Austin, Jericho (though he had good work in NJPW), Benoit (same) and I would contend that now Kurt Angle can be seen as an Icon. Some more icons who were more prominant outside of US though some have notable work in the states include Abdulah the Butcher, Mil Mascaras, El Santo, Jushin Liger, Dynamite Kid, Tiger Mask 1, Giant Baba, Jumbo, Inoki, Rikidozan Misawa, Kobashi, Muta and the list could go on