The phrase "ride an ass" has been used for centuries to refer to a person sitting on a donkey or a mule. However, there are numerous synonyms that are more appropriate to use in modern English. For instance, one can say "mount a horse" or "hop on a bike" to convey the same meaning. Other synonyms include "climb aboard," "straddle," "sit in the saddle," and "take the reins." These alternatives are more precise and convey a clearer image to the reader or listener. It is always advisable to use the correct synonym depending on the context to avoid conveying a wrong impression or message.