To cause someone to have doubts, worries, or concerns (about something); to introduce someone to a doubtful or worrisome idea. The candidate was doing very well in the polls six months ago, but it seems that this smear campaign has been effective in sowing a seed of doubt in the minds of voters.Recent economic turbulence in the Eurozone has sown the seed of doubt about the strength of the economy's recovery.Jim's suspicious behavior sowed a seed of doubt in Jenny's mind about his fidelity.