13-Letter Words Containing: _,E,I,R,S,S

• an instrument that indicates whether two periodic motions are synchronous (especially an instrument that enables a pilot to synchronize the propellers of a plane that has two or more engines)

• use an apostrophe

• a broad highway designed for high-speed traffic

• an extensive electronic network (such as the internet) used for the rapid transfer of sound and video and graphics in digital form

• to an inexpressible degree