1) one burning with zeal, a zealot
 2) used of God as jealous of any rival and sternly vindicating
    his control
 3) most eagerly desirous of, zealous for, a thing
    3a) to acquire a thing, (zealous of)
    3b) to defend and uphold a thing, vehemently contending for a thing

 From the time of the Maccabees there existed among the Jews a class
 of men, called Zealots, who vigorously adhered to the Mosaic law and
 endeavouring even by a resort to violence, after the example of
 Phinehas, to prevent religion from being violated by others; but in
 the latter days of the Jewish commonwealth they used their holy zeal
 as a pretext for the basest crimes.