Or search: tapered, lowering, dwindling, decreasing
2 Syllables: SU
hastening, labeling, rationing, straightening
3 Syllables: SUU
catering, Chamberlain, favoring, favouring, laboring, labouring, neighboring, neighbouring, tailoring, wavering
3 Syllables: USU
disabling, enabling
4 Syllables: USUU
awakening, endangering, occasioning, unwavering

Found 20 words across 4 groupings.