postmarking is postmark's Present Participle

postmark

US [ˈpoʊs(t)ˌmɑrk]
UK [ˈpəʊs(t)ˌmɑː(r)k]
  • n.邮戳
  • Web邮戳集萃;盖邮戳于;收藏
Simple Present:postmarks  Present Participle:postmarking  Past Tense:postmarked  
n.
1.
邮戳