a quick swim:
Are you coming in for a dip?
take/have a dip
Let's take a dip in the lake.
a slight decrease in the amount of something
an unexpected dip in profits
a thick mixture that you can dip food into before you eat it:
food[uncountable and countable]DFF
sour cream and onion dip
a place where the surface of something goes down suddenly, then goes up again
in a surface[countable]
a dip in the road
a chemical that kills insects on sheep and other animals:
for animals[uncountable and countable]HBATA
a stupid person
person[countable] American English spoken
a quick look at information, a book, magazine etc:
People interested in history would enjoy a dip into this book.