Portable is a relative term. In very old machinery portable meant the motor was attached. Stationary machines ran off flat belts with a separate power source. I have a 12" Red Star radial arm saw from the late 40s. The manual describes it as "easily carried by two men" for taking it to job sites. It has a cabinet on the bottom and weighs in the neighborhood of 200 pounds. 2 men might be able to carry it but it's not easy.
In your sewing machine's case portable just means it's in a carrying case and not a cabinet.
Rodney