Is ammonium hydroxide a strong base

No

Explanation:

Ammonium hydroxide is a weak base and not a strong base.

What is a base?

A base is any substance that interacts with water to produce or yield excess hydroxide ions in an aqueous solution.

A strong base is one that ionizes completely in solution. Most strong bases are hydroxides of alkali and alkaline earth metals.

A weak base is one that partially or slightly ionizes in an aqueous solution.

Such is ammonium hydroxide;

NH₃ + H₂O ⇄ NH₄⁺ + OH⁻

In the ionization of a weak base, the process results in an equilibrium reaction.