From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Giran shoots a tough, sticky, gooey, gum-like substance out of his mouth. The gum will fly towards his target and wrap around it.
Guru-guru-Gum was very tight like a straight jacket. If encased in it, the only way out was to break it with brute strength. Giran stated that the gum was so strong that not even he could break it. The more the victim struggled, the tighter the gum got. The gum could easily be broken by powerful fighters like Tambourine and Son Goku, who easily destroyed a dam made of the gum with a powerful Kamehameha.