Antonyms of adj open-and-shut

1 sense of open-and-shut

Sense 1
open-and-shut -- (so obvious as to be easily solved or decided; "an open-and-shut case")

INDIRECT (VIA obvious) -> unobvious -- (not immediately apparent; "in mathematical science connections are exhibited which...are extremely unobvious"- A.N.Whitehead)

Similarity of adj open-and-shut

1 sense of open-and-shut

Sense 1
open-and-shut -- (so obvious as to be easily solved or decided; "an open-and-shut case")
       => obvious (vs. unobvious) -- (easily perceived by the senses or grasped by the mind; "obvious errors")