Marianne Barton, 64, says she saw the creature just outside her house which is surrounded by three acres of land.
Stunned Marianne, of Chalford near Stroud, Glos, says the large creature leapt around 30ft in just a few bounds.
Marianne, an art and music event administrator said she had heard rustling and went to investigate.
She said: “As I watched and listened, a black animal, as far as one can tell colour in reduced light, jumped down from the wall and leapt with speed across the orchard 20 yards in front of me.
“Its flight across the garden was silent, and I would say it crossed the 30 feet or so of space ahead of me in no more than two or three bounds after landing from the wall”
“It was aiming for the corner where our garden borders our neighbour’s land.
“Its flight across the garden was silent, and I would say it crossed the 30 feet or so of space ahead of me in no more than two or three bounds after landing from the wall.
“I did not see it leave the garden because there were out buildings in the way, but I did hear the noise of what sounded like disturbed chickens from the direction it took.
“By the time I had got round the sheds there was no sign of it, which was as much as I expected.”
She claims the animal was the size of a large dog.
It also had a large extended tail and was fast moving like a cat or dog and was not to be confused with being a deer or any other animal.
She said: “My glimpse of the animal was fleeting, but it was the size of a large dog, with a long extended tail.
“It was bounding like a fast-moving cat or dog.
“It certainly was not a deer, a domestic cat, a dog, a fox, a muntjac or a badger. I did not clearly see the head, and I only had a side view.”
This is not Ms Barton’s first big cat sighting either.
She has lived in the area for two and a half years and a few months ago she spotted something similar.
Ms Barton said: “Some months earlier, when I went outside on a Tuesday evening to put out the rubbish which was again at dusk, I saw a similar animal run out from our woodland area, across our drive and down into the narrow valley below.
“Again this was Labrador sized, too large to be a fox or cat, and quite the wrong shape and gait to be a deer, muntjac or badger.
“I’ve been inclined to be sceptical as these things appear so quickly. However nothing else fits the description. I am prepared to be more open-minded now.”
Local wildlife enthusiast Frank Tunbridge has heard many accounts of big cat sightings coming in across the Stroud Valleys.
Frank said: “This is the latest sighting that I have had come in to me and it is very detailed.
“We have large cats living as part of the wildlife in the UK.
“There are many sightings of big cats in the Stroud Valleys due to people letting their exotic animals lose when the 1976 Dangerous Animals Act came in.
“Over the years these animals have adapted and are not large like lions or tigers.
“These animals are breeding true to type and it is found due to the uniform description of 80% of reports.
“They have changed their diet and lifestyle to suit the environment where they are.
“I get more reports from the Stroud Valleys than any other part of Gloucestershire.
“They are out there and existing on rabbits and pheasants and deer in the winter months.
“I must point out that I do not think that they will do any harm and in fact they should be protected.”
Natural England has stated it is confident there is no breeding big cat population in this country.
A spokesman said reports were occasionally received, but no sightings had ever been confirmed and evidence was unsubstantiated.