A person who laughs at everything, often uncontrollably and inappropriately, may be referred to as a "chronic laugher" or "involuntary laughter." In some cases, this behavior can be associated with a medical condition known as "pathological laughter" or "gelastic epilepsy." This condition causes episodes of uncontrollable and often inappropriate laughter due to brain abnormalities. However, it's important to note that not everyone who laughs frequently has a medical condition. Some people may simply have a very jovial and lighthearted personality, while others may use laughter as a coping mechanism. In such cases, they might be described as "having a hearty laugh" or "a person with an infectious laugh."