Bolshevik (n.)

"Russian radical socialist of the revolutionary period," 1917, from Russian bol'shevik (plural bol'sheviki), bol'shiy "greater," comparative of adjective bol'shoy "big, great" (as in Bolshoi Ballet), from Old Church Slavonic boljiji "larger," from PIE root *bel- "strong" (source also of Sanskrit balam "strength, force," Greek beltion "better," Phrygian balaios "big, fast," Old Irish odbal "strong," Welsh balch "proud;" Middle Dutch, Low German, Frisian pal "strong, firm").

The faction of the Russian Social Democratic Worker's Party after a split in 1903 that was either "larger" or "more extreme" (or both) than the Mensheviks (from Russian men'shij "less"); after they seized power in 1917, the name was applied generally to Russian communists, then also to anyone opposed to an existing order or social system. Bolshevism is recorded from 1917.

updated on October 10, 2017

Definitions of Bolshevik from WordNet
Bolshevik (n.)
emotionally charged terms used to refer to extreme radicals or revolutionaries;
Synonyms: Marxist / red / bolshie / bolshy
Bolshevik (n.)
a Russian member of the left-wing majority group that followed Lenin and eventually became the Russian communist party;
Synonyms: Bolshevist
Bolshevik (adj.)
of or relating to Bolshevism;
Synonyms: Bolshevist / Bolshevistic
From, not affiliated with etymonline.