Urban Dictionary definitions: used mostly in the 80's to describe something awesome or excellent, surfer slang describing waves, the whitest word on the face of the earth except for gnarly that means AWESOME or sweet.
Ways to use it in a sentence:
That's totally tubular, dude!
I got an 'A' on that basket weaving test. Tubular!
Man, that wave I hit was TUBULAR!
That ride was tubular, man. Did you catch that?!
Nate surprised us with tractor tire tubes. I thought they were for lazily floating along with a book but I was so wrong. Worth every penny, the possibilities are endless. Dude.