Birdman's putting his palace of a home up for sale again after more than a year without a successful bite -- which means one thing ... BIG discount! Relatively speaking, anyway.

The Cash Money honcho is listing his Miami beachfront mansion -- which is located on the secluded Palm Island -- for $15.5 million. Sounds like a ton of cash -- 'cause it is -- but hey, it was going for $20 mil last year. The place has been on and off the market since then.

If you're a picky multi-millionaire, the price might just be right this time around.

At almost 20,000 square feet, the house features 10 bedrooms, guest suites, a private beach volleyball court, 2 wine cellars, a movie theater and a chef's kitchen with a pizza oven. Basically, it's the definition of living large and lavish.