"Seat width" refers to the measurement of how wide a seat is. It tells you how much space you have to sit comfortably without feeling cramped. Full definition
With just 31 ″ of seat pitch and 17 ″ of seat width this isn't the most comfortable of cabins by any stretch of the imagination. (travelingformiles.com)
Also the entire row is slightly narrower than the rows forward - very slightly reducing seat width compared to the remainder of the PE cabin. (seatguru.com)
Also didn't have a problem at all with seat width. (seatguru.com)