parading of portable shrines and floats at Shinto festivals
Refers to the ceremonial procession of mikoshi (portable shrines) and dashi (floats) during Shinto festivals, often accompanied by chanting and music.
The climax of the festival is the parading of the portable shrines.
お練り is the customary, slightly more formal term specifically for the shrine-parade sense, while 練り alone is more general and also covers kneading or paste.
The honorific prefix お is attached to the noun 練り (from 練る, 'to knead' or 'to parade'), referring to the ceremonial procession. The exact historical derivation is uncertain.