Porthole
A porthole was an opening in a hull or bulkhead of a sailing vessel, or such spacecraft as a Bajoran lightship. 

Arjin, a hopeful Trill initiate who was training with Jadzia Dax in 2370, who believed he had made a huge mistake that jeopardized his chances of succeeded towards his goal of being joined, confessed to Quark that he "just threw my whole life out a porthole." ()

When Benjamin Sisko constructed a Bajoran lightship in 2373, looking out the portholes was the only way he could see what was going on around his ship while in flight. ()

See also 
 Viewport

External link 
 

Spacecraft components