The fifth and typically highest gear of an engine.

(music theory) A sequence of bass notes at intervals of a perfect fifth lower than the previous note. In equal temperament the sequence repeats every twelve tones, forming a cycle.

(cricket) The slip fielding position beyond the fourth slip.

(road transport) A type of trailer hitch, which consists of a horseshoe-shaped plate on a multidirectional pivot, with a locking pin to couple with the kingpin of a truck trailer.

(idiomatic) To decline to comment, especially on grounds that it might be incriminating.

The fifth amendment to the United States Constitution, which covers several rights, but is used most often quoted regarding the right against self-incrimination.

(slang) An 1800-ml bottle of spirits, especially sake.

(US, education) The period in school that comes after fourth grade and before sixth grade.

A group of people which clandestinely undermines a larger group, such as a nation, to which it is expected to be loyal. / Used other than figuratively or idiomatically: see fifth, column.

(medicine) The manifestation as rashes of an infection by erythrovirus.