A psychotic break is a (layman) term used to describe the first time that a person experiences an episode of primary psychosis. Many different kinds of psychoactive drugs are known to cause psychotic breaks. Examples are LSD, dextromethorphan(in higher doses), pcp, and opiates(mainly from experincing withdraw symptoms).
Though pretty much anything else can cause temporary psychosis depending on the morals of the individual. Simply feelings of fear, abandonment, or guilt could cause an individual to suffer from temporary psychosis. Symptoms of psychotic breaks vary greatly, usually depending on the circumstanses of diagnosis or any substance injested that might of contributed.
Symptoms can range from harmless, sometimes "unnoticed" delusions, to violent out bursts and major depression. Psychiatrists may informally use the term "psychotic break" in hindsight to describe the first episode of psychosis in a patient who has been diagnosed with the chronic condition of schizophrenia.