Boyd’s Bible Dictionary:
(zealous). A name added to that of the apostle Simon to distinguish him from Simon Peter, and to emphasize his membership of the party of Zealots (Luke 6:15). [SIMON, 4.]
Concise Bible Dictionary:
See SIMON No. 2.
Strong’s Dictionary of Greek Words:
Meaning:
the same as 2207; a Zealot, i.e. (specially) partisan for Jewish political independence
Jackson’s Dictionary of Scripture Proper Names:
a zealot (especially for Jewish independence)
Potts’ Bible Proper Names:
Zealous; full of zeal; jealous:― applied to Simon, Luke 6:15. {Zelotes}