A cloverleaf segment is a type of highway interchange that consists of two loop ramps that allow vehicles to enter and exit the highway in a safe and efficient manner. The term 'cloverleaf segment' is derived from the shape of the ramps, which resemble the leaves of a four-leaf clover. The crossword solution for this term is 'RAMP, ' which refers to the loop ramps that make up the cloverleaf segment.