Strictly speaking, a linear pattern, as the name suggests, is any pattern whose individual voices never appear in unison. In real terms, the name is used on patterns which predominantly adhere to the above. Linear patterns are usually very syncopated and occur most often in Funk and Jazz Fusion music.
One way to create a linear pattern:
Here is a sticking pattern made up of the paradiddle and an inversion. (beat 6 becomes beat 1).
Here is a bass drum rhythm.
Here is the composite pattern.
The final linear pattern featuring snare accents on beats 2 and 4.