What does "iceberg lettuce" mean?

A lettuce cultivar (Lactuca sativa var. capitata) noted for its crunchiness; the most familiar of all lettuces sold in the United States.

What is a synonym for "iceberg lettuce"?

Common synonyms include: crisphead lettuce, iceberg.

noun

noun ·Rare ·Advanced level

Noun

1
A lettuce cultivar (Lactuca sativa var. capitata) noted for its crunchiness; the most familiar of all lettuces sold in the United States. countable, uncountable
"I wonder how many of the readers of AMERICAN GARDENING have tried the Iceberg lettuce."
2
lettuce with crisp tightly packed light-green leaves in a firm head wordnet

"I wonder how many of the readers of AMERICAN GARDENING have tried the Iceberg lettuce."

Apparently originally a trade name.