1. In geometry, relating to or being lines, planes, or curved surfaces that are always the same distance apart and therefore never meet: The notebook that Susan bought had parallel or horizontal lines which helped her do her homework.

Parallel means literally "beside each other".
2. Relating to two things that are comparable because they are similar and share many characteristics: The two parallel events were both concerts and took place at the same time of day.

Something or someone that possesses the property of being analogous to another thing or person: Shirley was certainly a parallel to her sister who looked exactly like her because she had the same eye and hair color, stature, and personality.

The connecting of two or more series of circuits in parallel.