suckerish

adjective2

1. •
   (informal) Gullible; easily taken advantage of.

   • He even forgets about the great sum he loses, but perpetually irritates himself with his own suckerish imagination. — 1934
2. •
   Resembling or characteristic of the sucker of an animal.

   • […] plans, plans, plans, spreading outward from my hard skull, but in the soft and suckerish manner of an octopus. — 1995