tapering
ta-per-ing
verb
Becoming gradually narrower or thinner towards one end; reducing in amount.
"The road was tapering as we drove on."
adjective
Gradually narrowing or thinning towards one end; becoming progressively smaller.
"The tapering spire reached high into the sky."
Thesaurus
Synonyms: narrowing, tapered, narrow, tapering off, decreasing, dwindling