From Outscape Wiki
This is a fantasy term first coined by Poul Anderson in his "Trader to the Stars" series to reflect a kind of warp drive where the ship remains at sub light speeds but warps space ahead and behind it to effectively travel faster than light. So its "Pseudo Speed" may be say 16x the speed of light to determine how much distance it is travelling but its thruster speed may be considerably less than "C" (Usual abbreviation for light speed)
This kind of warp drive has been mathematically shown to be possible In theory by modern science. See Alcubierre Drive on Wikipedia for example.
As the engines in Outscape are referred to as Warp Drives it is reasonable to assume they are based on a parallel technology to this theory