also: かもめ〜る
noun
summer greeting card with lottery ticket
A seasonal product sold by Japan Post from June each year; combines a summer greeting (暑中見舞い) with a built-in lottery number.
今年もかもめーるを買って、友達に送ろう。
Let's buy some kamome-ru this year too and send them to friends.
かもめーるの抽選番号を確認したら、当たっていた。
When I checked the lottery number on my kamome-ru, I had won.
Portmanteau of かもめ (seagull) and メール (mail), with the long vowel mark suggesting the product name. The exact derivation is uncertain beyond the brand naming.