'Undertone' definitions:

Definition of 'undertone'

From: WordNet
noun
A quiet or hushed tone of voice; "spoke in undertones"
noun
A subdued emotional quality underlying an utterance; implicit meaning [syn: undertone, undercurrent]
noun
A pale or subdued color [syn: undertone, tinge]

Definition of 'Undertone'

From: GCIDE
  • Undertone \Un"der*tone`\, n. A low or subdued tone or utterance; a tone less loud than usual. [1913 Webster]

Synonyms of 'undertone'

From: Moby Thesaurus