Glottal is an adjective that means producing a sound from the glottis.
The Greek word glottis refers to ‘the tongue.’ After being imported into English, it’s meaning shifted to refer to the larynx, a part of the vocal cords that effect voice modulation. To make a glottal sound is to make a sound that involves this part of the body. This often can refer to a clicking sound.
After my throat surgery, I struggled to make any glottal sounds. It seemed my glottis had simply been irreversibly damaged.