This returns a map without the key-value pairs for the keys mentioned in the function argument. It can be used to remove information from existing map.

(dissoc {:a 1 :b 2} :a) ;; {:b 2}

It can also be used for dissocing multiple keys as:

(dissoc {:a 1 :b 2 :c 3} :a :b) ;; {:c 3}