1. To be able to take part in sexual activity following a period of time where one could not due to medical or personal issues.
2. To serve a purpose related to sex.
Following the birth of their son, Bill hoped his wife would be fucktional again sooner than she was for the birth of their daughter when he went four months without sex.
A sexual experience that is planned in advance and set up to be different or weird on purpose.
She was bored enough to take up his suggestion for existentialist sex and wore the moon boots and feather boa.