ˈunderswell [under-1 5 c.] A swell below the surface; an undercurrent. 1849Tait's Mag. XVI. 760 This placid springtime of life had a strong underswell of sorrow.1894Cycl.Rev. Current Hist. (Buffalo, N.Y.) IV. 733 A certain insistence of tone which gives note of a strong underswell of feeling and purpose.