(as) slow as molasses
US /əz sloʊ əz məˈlæsɪz/
UK /əz sloʊ əz məˈlæsɪz/

1.
慢如蜗牛, 非常慢
extremely slow; moving or happening at a very low speed
:
•
The old computer runs as slow as molasses.
这台旧电脑运行得慢如蜗牛。
•
Traffic was moving as slow as molasses on the highway.
高速公路上的交通慢如蜗牛。