What does the word undercurrent mean?

Usage examples for undercurrent

  1. There was an undercurrent of nervousness, discernible only to her eyes. – Love and Lucy by Maurice Henry Hewlett
  2. Look below the surface and you will find, in all of them, an undercurrent of keen spirituality- a nucleus of half a dozen widely read and thoughtful men, who foster the best traditions of the mind. – Old Calabria by Norman Douglas
  3. The first evening there was an undercurrent of excitement in the air; there were to be cutlets for dinner. – By Desert Ways to Baghdad by Louisa Jebb