An example sentence using the word "retrogress" is "the quality of research at the university lab has begun to retrogress since the massive budget cuts went into effect." This example comes from Merriam-Webster.
"Retrogress" means to move backward. It is a synonym to regress, return and revert, and several related words include backslide, relapse, worsen and decline. Sentences involving the word retrogress describe how something has returned to how it was at an earlier point in time. Retrogress has negative connotations when used in a sentence describing how something that has improved or expanded over time has reverted to an earlier state. An example from the Oxford dictionary is "she retrogressed to the starting point of her rehabilitation."