I was running on an unused logging road and came up behind a wild cat. It didn't see me coming, so I got pretty close, maybe 20 feet away. It turned and stared at me for a second and then took off up a steep hill.
It was about 2.5 feet to the top of it's head, a little smaller than a Labrador. It wasn't a bobcat or lynx, because it had a long tail, but I don't think it was long enough to be a mountain lions tail(I don't remember seeing it curled). It had a brown coat and the tail had a stripey bit at the tip. 100% a cat from the body shape and movement.
But after looking it up, it seems like mountain lions basically don't exist in new england, or at least are extremely rare. Its limbs were not as thick as the mountain lion images I'm finding online.
I thought maybe it was one of those megasized housecats, but this trail is separated from town by a deep and wide river, any housecat would have had to walk 3 miles and across 2 bridges(one of which is a metal mesh footbridge) or 7 miles along the logging road to get to the nearest house. It's also below freezing out and there's 5+ inches of snow on the ground.
It's making me feel like I hallucinated this or something, because it doesn't seem possible. Hopefully I'll see it again now that I've looked at a ton of wild cat pictures. I was trying to remember as much detail as possible when I saw it, but I didn't know what to look for.
All the wild/domestic hybrids have pretty striking coat patterns (Bengals have rosettes like jaguars or leopards, and Savannah Cats look just like their Serval ancestors), so if it was just brown, that's probably unlikely. The only normal-ish cat that might get to be almost the size of a Labrador would be a Serval (or maybe a very large F1 Savannah male), and the coat definitely would have stood out on either of those. A mountain lion out of its normal range seems like by far the most likely explanation to me. Could be a younger male who is wandering in search of territory.