#Clojure, 21 bytes

(defmacro a[]`(a))(a) 

Ties up the compiler by defining a macro that repeatedly emits calls to itself.

On my phone, this causes the REPL to hang and lag the device. On my laptop, this fails outright with a StackOverflow.

Unfortunately the StackOverflow happens instantly, but it's still valid according to the rules.

Clojure, 21 bytes

(defmacro a[]`(a))(a) 

Ties up the compiler by defining a macro that repeatedly emits calls to itself.

On my phone, this causes the REPL to hang and lag the device. On my laptop, this fails outright with a StackOverflow.

Unfortunately the StackOverflow happens instantly, but it's still valid according to the rules.

#Clojure, 21 bytes

(defmacro a[]`(a))(a) 

Defines a macro that repeatedly emits calls to itself.

On my phone, this causes the REPL to hang and lag the device. On my laptop, this fails outright with a StackOverflow.

Unfortunately the StackOverflow happens instantly, but it's still valid according to the rules.

#Clojure, 21 bytes

(defmacro a[]`(a))(a) 

Ties up the compiler by defining a macro that repeatedly emits calls to itself.

On my phone, this causes the REPL to hang and lag the device. On my laptop, this fails outright with a StackOverflow.

Unfortunately the StackOverflow happens instantly, but it's still valid according to the rules.

#Clojure, 21 bytes

(defmacro a[]`(a))(a) 

Defines a macro that repeatedly emits calls to itself.

On my phone, this causes the REPL to hang and lag the device. On my laptop, this fails outright with a StackOverflow.

#Clojure, 21 bytes

(defmacro a[]`(a))(a) 

Defines a macro that repeatedly emits calls to itself.

On my phone, this causes the REPL to hang and lag the device. On my laptop, this fails outright with a StackOverflow.

Unfortunately the StackOverflow happens instantly, but it's still valid according to the rules.