One as to the validity of which there exists some doubt, either asto matter of fact or of law; one which invites or exposes the party holding it tolitigation. Distinguished from a “marketable” title, which is of such a character that thecourts will compel its acceptance by a purchaser who has agreed to buy the property orhas bid it in at public sale. Herman v. Somers, 158 Pa. 424, 27 Atl. 1050, 38 Am. St Rep. 851.