obsessor (noun M) : id.
* One who sits, stays, abides in a place; a frequenter, haunter.
* In gen. (only ante-class. and poet.): hoc ego fui hodie solus obsessor fori,sai in the forum alone,Plaut. Ps. 3, 2, 18: vivarum aquarum (of a water-snake), Ov. F. 2, 259.
* In partic., milit., a besieger, invester, blockader: obsessor curiae,Cic. Dom. 5, 13: Luceriae,Liv. 9, 15, 3: plus pavoris obsessis quam obsessoribus intulit,Tac. H. 3, 73.

s. TLL