A no call, no show is an American term for absence from the workforce without notifying the employer.
[1] When workers miss work, (especially in jobs in which one's workload would require to be substituted for the day, such as teachers, cashiers, servers, etc.
Many businesses have forms of disciplinary actions as a result of no call, no shows, such as counseling statements, suspension, and possibly dismissal.
[2] When a no call, no show is not preventable, such as when an employee suffers a medical emergency and is unable to inform their employer, satisfactory documentation of the situation is expected.
In the United States, the Family and Medical Leave Act of 1993 (FMLA) allows employees to take unpaid leave during specifics situations such as medical issues, but they still must comply with attendance policy.