Rectilineally is an adverb that has the meaning of being straight ahead or along a straight line. There are few synonyms that have the same meaning as rectilineally, such as linearly, directly, straightforwardly, plainly, and evenly. These synonyms indicate that something is moving in a straight line without any twists or turns. Linearly suggests a relationship between two or more points or positions on a plane. Directly, on the other hand, means without interruption or delay in a direct passage. Straightforwardly means that something is simple and easy to understand, while plainly suggests that something is explicitly stated. Lastly, evenly suggests that something is constant or uniform, either in motion or intensity.