Of a place where one can go; from pro/seimi (ei)=mi "go").
Here masculine accusative singular or neuter nominative/accusative singular, with same or similar glossing in other lexica. Evidently quoted from somewhere -- perhaps Josephus, Jewish War, where the word occurs several times, e.g. 5.141 (web address 1), but see also e.g. Strabo 6.2.8 (web address 2).
For the opposite, see alpha 3698.