Learn how to say Precession correctly in English with this tutorial pronunciation video.
Oxford dictionary definition of the word precession:
[mass noun] Physics
the slow movement of the axis of a spinning body around another axis due to a torque (such as gravitational influence) acting to change the direction of the first axis. It is seen in the circle slowly traced out by the pole of a spinning gyroscope.
late 16th century (as a term in astronomy, referring to the precession of the equinoxes): from late Latin praecessio(n-), from praecedere ‘go before’ (see precede)