Where do you throw away trash too big to fit into your roadside trash bin, besides dumpsters? Where do you throw away something approximately as large as professional size...
Where do you throw away something approximately as large as professional size basketball backboard?
Most towns hold seperate pick up for such things, you sit it out at the curb, call sanitation and ask. You could also rob it to the landfill (city dump).
Waste Management is everywhere.
http://www.wastemanagement.com/
Answers: You don't. You appropriate it directly to the dump and pay to hold them take it.
Okay, that's a bit difficult. Is it completely unusable - as in cracked and breaking? Why not verbs to break it apart? Smash it into small pieces and then it will fit within your can.
Another idea is to try and recycle it. If it is contained by decent condition, try posting it on freecycle and see what happen.
Oh yeah, some towns have a "Spring cleanup" that will tolerate you drop off hefty trash at certain deposit places, sometimes for a allowance, sometimes for free. Find someone with a truck to back you haul it sour to the deposit sites.
But don't find someone else's dumpster and put it in behind at night when not a soul is looking. That's kind of rude.