help- what is tear-ing?

[katbret]

While dining in a fabulous B&B last month in a small town just south of Macon, GA. I sampled 2 fine Merlots- a Shafer & a Sterling. We were dining with a large party & the waiter suggested we try a Cab that was bodied similar to that of a Merlot. (I do not remember the name - I was not that impressed with the flavor.)Someone else commented that they could tell it was a CAB by the way the wine "tiered" - "teared" sp?
I did not wish to show my ignorance & simply agreed with a nod & sipped the new vino silently. PLEASE HELP- WHAT was he describing - how can you immediately tell a Merlot from a Cabernet- simply by looking?
I would think flavor & smell would HAVE to factor in as well?!
Thanks- KATSY