bride's silk floss headdress
Traditional white hood worn by a bride in a Shinto wedding, covering the head and often part of the face.
The bride wore a watabōshi for the Shinto wedding ceremony.
clumps of snow on branches, stones, etc.
Describes snow that has accumulated in soft, rounded shapes resembling a traditional bridal hood.
Snow had piled up on the branches like watabōshi.
Compound of 綿 (wata, 'cotton') and 帽子 (bōshi, 'hat'). The second sense is a metaphorical extension based on the shape.