Answer:

tetrads

Answer	Crossword Clue
TETRADS	Groups of four
TETRADS	The Horsemen et al.
TETRADS	The Beatles and others

TETRADS	Bridge units
TETRADS	Foursomes
TETRADS	Quartets.
TETRADS	Double duos
TETRADS	Quaternities

Crossword

a puzzle consisting of a grid of squares and blanks into which words crossing vertically and horizontally are written according to clues.