iota
dash
A four letter word meaning not kosher is: tref
kill
aver
into
The word pine can have that meaning.
Microscopic
A four-letter word for cooking fat is "lard".
A four letter word meaning to grow light as the sun rises is dawn.
Isle
A "bay" is a small protected body of water that is a four-letter word.
A four letter word meaning the foundation of something is base.