Manufactured weapons are (most) non-natural weapons
Unfortunately, Pathfinder/Paizo does not appear to have ever actually rigorously defined what a manufactured weapon is (nor was there a precise definition given in the preceding D&D 3/3.5e), so we're forced to extrapolate by context and from language what is meant. However, the rules do so frequently refer to effects applying to "natural weapons or manufactured weapons", seemingly meaning to encompass "any weapon", that the conclusion largely drawn by the player base - and supported by the definition of the word "manufacture" - is that a manufactured weapon is any crafted, non-natural weapon.
The relevant definition of the verb "to manufacture":
to make from raw materials by hand or by machinery
So in Pathfinder a manufactured weapon is most any non-natural weapon, barring the edge cases which involve unarmed strikes (considered manufactured, except a monk's unarmed strikes are also natural weapons when convenient) or magically created weapons which are clearly not natural but also possibly not manufactured.
You could peruse this thread from Paizo's forums if you want to observe some players arguing about the definition of manufactured weapons; you'll note that though they disagree on whether or not certain spells/magical abilities should constitute manufactured weapons or not, none of them are working from a definition which excludes a mundane, non-masterwork longsword from being a manufactured weapon.