from The American Heritage® Dictionary of the English Language, 4th Edition
- n. The continuous line or surface including all the points in space reached by a wave or vibration at the same instant as it travels through a medium.
from the GNU version of the Collaborative International Dictionary of English
- n. the surface of initial displacement of the particles in a medium, as a wave of vibration advances.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. (physics) an imaginary surface joining all points in space that are reached at the same instant by a wave propagating through a medium
- n. all the points just reached by a wave as it propagates
Sorry, no etymologies found.
The explosion's main wave front would indeed be well past the asteroid by now, but there would also be slower but still dangerous debris expanding outward behind that front.