Off-Round
A catch-all for pearls that aim at round and miss. Covers semi-round through roundish.
Off-round is a grading description rather than a shape a seller advertises. It means the pearl deviates measurably from a sphere but is not irregular enough to be baroque.
The practical test is the roll. Off-round pearls wobble; baroque pearls do not roll at all.
When you are buying
If a listing calls pearls off-round, that is a seller being straight with you. It is a more honest description than round on most freshwater strands.
Semi-Round
Very slightly out of true: round to the eye, measurably not. The best value in the whole shape range.
Roundish
Recognisably round in outline but visibly imperfect on close inspection.
Round
A true sphere. The rarest and most expensive pearl shape, and the benchmark every other shape is priced against.
Baroque
Any pearl with no axis of symmetry. Once treated as a reject, now the shape most associated with contemporary pearl design.