Sober means having a blood alcohol concentration (BAC) of 0.00, not being under the influence of illicit drugs, and being in a proper state to enforce your duty of care to alcohol recipients. According to the Merriam-Webster dictionary, the definition of sober is not intoxication or abstaining from intoxicating drugs or drinking alcohol. Being sober can also mean refraining from using any addictive substance. Developed by Black's Law Dictionary, 2nd ed.
Some common synonyms for sober are serious, serious, sedated, serious, solemn, and serious. While all of these words don't mean light or frivolous, sober emphasizes the seriousness of purpose and the absence of frivolity or frivolity.