flagellar motor

Richard DawkinsのThe God Delusionを読んでいます。
In Climbing Mount Improbable, I expressed the point in a parable. One side of the mountain is a sheer cliff, impossible to climb, but on the other side is a gentle slope to the summit. On the summit sits a complex device such as an eye or a bacterial flagellar motor.
文章から "flagellar" は鞭毛の事だと分かりますが、知らなかったので辞書で確認します。
・Oxford English Dictionary: A slender threadlike structure, especially a microscopic appendage that enables many protozoa, bacteria, spermatozoa, etc. to swim.: The single flagellum provides the bacteria with mobility and kinetic activity.
・Collins Dictionary: a long whiplike outgrowth from a cell that acts as an organ of locomotion: occurs in some protozoans, gametes, spores, etc