From The Collaborative International Dictionary of English v.0.48 :
Side-slip \Side"-slip`\, v. i.
See Skid, below.
[Webster 1913 Suppl.]
From WordNet (r) 3.0 (2006) :
sideslip
n 1: an unexpected slide [syn: skid, slip, sideslip]
2: a flight maneuver; aircraft slides sideways in the air [syn:
slip, sideslip]