What is the definition of spastic laryngitis?

Not a medical term: "spastic laryngitis" is not a medical term. Most likely you are referring to spasmodic dysphonia. This is a voice disorder characterized by spasm of the voice box muscles. It results in a choppy, broken sounding voice. It can be treated with voice therapy and/or botulinum toxin (botox). This disorder is best treated by an ENT with experience in this disorder. Best wishes.

Spasmodic dysphonia: You may be speaking about "spasmodic dysphonia" which is a disease of the communication between the brain and the nerves to the voicebox. This disorder is best diagnosed by a physician but you can find samples of how those with it sound online, i'm sure. Either way, any one with 'spastic laryngitis' sounds like they need an expert in voice.