Semi-washed is a processing description whose meaning should be checked with the producer or seller. The source describes a mechanical step that removes the cherry skin and some or most of the sticky mucilage surrounding the coffee seed. It places the approach between familiar descriptions of washed and pulped-natural processing.
That explanation helps identify the operation, but it does not settle every detail of fermentation, washing or drying. Processing language is not perfectly uniform across regions, and a label can conceal important practical differences.
For a purchase, ask what was removed, when the coffee was dried and what specific flavor description the roaster gives for that lot. The source associates semi-washed coffee with a relatively clean, lively cup, yet that should remain a broad expectation rather than a guarantee. Compare the actual brewed result using a consistent recipe. Origin, variety, roast and handling continue to matter after the processing category has been named.
The conversation
A good question can make a better brew.