Real Dictionary

parallel
adjective: If two lines, two objects, or two lines of movement are parallel, they are the same distance apart along their whole length.
adjective: Parallel events or situations happen at the same time as one another, or are similar to one another.
countable noun: A parallel is an imaginary line round the Earth that is parallel to the equator. Parallels are shown on maps.
countable noun: If something has a parallel, it is similar to something else, but exists or happens in a different place or at a different time. If it has no parallel or is without parallel, it is not similar to anything else.
countable noun: If there are parallels between two things, they are similar in some ways.
verb: If one thing parallels another, they happen at the same time or are similar, and often seem to be connected.

parallel in American English
extending in the same direction and at the same distance apart at every point, so as never to meet, as lines, planes, etc.
adjective: extending in the same direction, equidistant at all points, and never converging or diverging
noun: a parallel line or plane
transitive verb: to provide or show a parallel for; match

parallel in British English
adjective: separated by an equal distance at every point; never touching or intersecting