It means fastest.
more rapidly and most rapidly
more rapidly, most rapidly
Rapidly means quickly, taking place at an accelerated rate.
Weathering attacks the surface of the rock most rapidly.
means do it fast
Growing rapidly in number.
if you mean rapidly (note the spelling) it means 'quickly'
Water is depleted most rapidly during physical exercise
service -nova net
If you mean what two element types then: Metals and non-metals If not, I do not know what you are asking
Jupiter at 9h 55 mins to make one turn, is the most rapidly turning out of all eight planets.
Rapidly means quickly, taking place at an accelerated rate.