This is a word that probably derives from the root patar, meaning "to conclude", "to terminate". It specifically indicates that brief portion of the books of the Prophets and/or the Writings that follows the reading of the Torah portion (parashah) in the synagogue ritual on Shabbat and holy days.
There is always a connection, more or less explicit, between the chapter of the Torah portion being read and the passage from the prophetic text, or the Writings, that accompanies it.
Source: "Gli ebrei questi sconosciuti" by Elena Loewenthal