1) a spy, scout
2) under the emperors an attendant and member of the body guard, employed as messengers, watchers, and executioners
3) the name is transferred to an attendant of Herod Antipas that acted as executioner
Part of Speech: noun masculine
Of Latin origin; a speculator, that is, military scout (spy or [by extension] life guardsman): - executioner.
These two sites give similar information, with the definition from several dictionaries and statistics on the use of the word.
Perseus Digital Library
University of Chicago's Logion lexicon
Thayer's dictionary plus other information.
From this site's dictionary (in Italian)
Click on the first column to search for that word as a form of the root σπεκουλάτωρ; click on the second column to search for that grammatical form of the root σπεκουλάτωρ; click on the third column to search for that word and grammatical form; click on the total to search for the root σπεκουλάτωρ.