Right so I'm mostly into hauntings and that sort of thing but this category genuinely fascinates me too because there's so much crossover between big black creature sightings and what some researchers call interdimensional entities. Like people assume it has to be a physical animal but what if it isn't?
Where abouts are you in the country? Cheshire here and we get the odd big cat report now and then but what you're describing sounds way bigger than that. Did it move in a weird way or more like a normal animal would? That detail tends to separate the mundane stuff from the genuinely strange cases.
Also did you feel anything before or after seeing it, like a sense of dread or pressure in your ears? That comes up a lot in these sightings and I think its worth paying attention to.