What does 封 (fēng) mean in English?

Card 216HSK Level 1216/1034
CARD216
PROGRESS21%
封
fēng
for letters(Measure Word)
Click to reveal
← Previous↑ DeckNext →

Reveal: Click/Space/Enter/↑↓/w/s/j/k•Navigate: ←→/h/l/a/d