A suspension is a mixture in which the particles are only temporarily suspended and will settle out. A good example is the "snow" particles in a holiday snow globe.
In Geography suspension is when rocks in rivers are carried along by the river . It generally means , when fine , light material is carried along by the river bed . There are other types of transport...
1) that you're supposed to take it orally (by mouth) and 2) that it's a suspension (a sort of slurry) instead of a solution or a tablet or what have you.