What is a Bumpy Word™?

Question

_{This is in the spirit of the What is a Word/Phrase™ series started by JLee with a special brand of Phrase™ and Word™ puzzles.}

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If a word has a certain property, I call it a Bumpy Word™.

You can use the examples below to find the property:

Bumpy™	Not Bumpy™
ARMY	NAVY
BUMPING	JERKING
CABAL	CONSPIRACY
CHASER	PURSUER
COALESCE	SOLIDIFY
COMPOSITE	DIVERSE
CRANK	TURN
CRAZY	INSANE
EXAMINATION	TEST
FERAL	UNCIVILIZED
HIGHER	GREATER
JUMPING	LEAPING
ORATOR	SPEAKER
QUALITATIVE	SUBJECTIVE
SQUASH	CRUSH
THRASH	SPASM
TRUSTING	BELIEVING
UPWARD	SKYBOUND
VAULTING	CAVERNOUS
WELDED	FUSED

Here is a CSV version:

Bumpy™,Not Bumpy™
ARMY,NAVY
BUMPING,JERKING
CABAL,CONSPIRACY
CHASER,PURSUER
COALESCE,SOLIDIFY
COMPOSITE,DIVERSE
CRANK,TURN
CRAZY,INSANE
EXAMINATION,TEST
FERAL,UNCIVILIZED
HIGHER,GREATER
JUMPING,LEAPING
ORATOR,SPEAKER
QUALITATIVE,SUBJECTIVE
SQUASH,CRUSH
THRASH,SPASM
TRUSTING,BELIEVING
UPWARD,SKYBOUND
VAULTING,CAVERNOUS
WELDED,FUSED

Answer 1

In a word,

If a letter occurs (in the alphabet) later than the previous letter in the word, let us call it a "rise", otherwise, it's called a "fall". Note that the first letter of a word is neither of these.

Then a Bumpy word is

A word in which "rise"s and "fall"s occur alternately.

Example:

A,R(rise),M(fall),Y(rise) | N,A(fall),V(rise),Y(rise).

Why "Bumpy"?

For a Bumpy word, imagine plotting the letter-indexes in the order they occur in the word. For example, "BUMPING" would be plotted as follows:

Alternation between "rise" and "fall" obviously means that the graph is more "uneven" or "bumpy".