Which of the following medications is known as a rescue inhaler?

Terbutaline is classified as a rescue inhaler because it is a short-acting beta-agonist (SABA) that provides rapid relief from acute bronchospasm associated with asthma or other respiratory conditions. These inhalers work by relaxing the muscles of the airways, allowing for easier airflow and immediate relief from symptoms such as wheezing and shortness of breath.

In contrast, the other options listed are corticosteroids, which are used for long-term management and control of inflammation in respiratory conditions rather than for immediate relief. Medications like Budesonide, Beclomethasone, and Ciclesonide are designed to be used on a regular schedule to reduce chronic inflammation and prevent asthma attacks, but they do not provide the same rapid relief as a rescue inhaler like Terbutaline.