Or search: lb, cat, dram, pound, drachm, drachma
2 Syllables: SU
boundless, bounteous, brownish, Countess, countless, fountains, groundless, mountains, roundness, soundest, soundings, soundness
3 Syllables: USU
announces, denounces, profoundest, pronounces, renounces, surroundings

Found 18 words across 2 groupings. Skipped 1 excess word of a similar stem.