The priorities of Grand (not at all) Ayatullah Sistani: "1596. If a person forgets that he is observing fast and commits sexual intercourse or he is compelled to have sexual intercourse in a manner that makes him helpless*, his fast does not become void. However, if he remembers (that he is observing fast) or ceases to be helpless during sexual intercourse, he should withdraw from the sexual intercourse at once, and if he does not, his fast becomes void."
*What does he mean here?