Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. pessŭlum, i, n. dim. [pessum], a pessary, Cael. Aur. Acut. 3, 18, 184.
pessŭlus, i, m. (neutr. collat. form in plur. pessula, Paul. Nol. Carm. 18, 412) [πάσσαλος], a bolt (ante- and post-class.): occlude sis fores ambobus pessulis, Plaut. Aul. 1, 2, 25: pessuli, heus pessuli, vos saluto, id. Curc. 1, 2, 60: pessulum ostio obdo, shoot the bolt, lock the door, Ter. Eun. 3, 5, 55: foribus, id. Heaut. 2, 3, 37: pessulos inicere, to shoot the bolts, App. M. 3, p. 135, 39; 1, p. 107, 12; p. 108, 24: aperire: pessulum ostii mei aperui dilecto meo, Vulg. Cant. 5, 6.