A form of sex education that advocates only abstinence as a means to avoid pregnancy and sexually transmitted diseases.

(computing) A permission to access files or directories where the user is only allowed to read or view, not to make changes.

plural of read-only memory

(rail transport) The operation of a train without a conductor or guard as a cost-cutting measure; one-man operation.

If somebody at the top of an abusive hierarchy was aware of the abuses, they might take action to stop them.

plural of write-only memory

(computing) A type of computer memory to which data can be written, but from which it cannot be read. / (informal) A failed or otherwise inoperative memory device.

(cryptography) An attack on a cryptosystem that relies only on the attacker's knowledge of some ciphertexts encrypted with that system and key. Less powerful than a known-plaintext attack.

Alternative form of God knows (“it is unknown to people”)

Alternative form of God knows, in sense of something unknown to mortal men.