From Destinypedia, the Destiny wiki
Intrinsic Traits are special perks always found on a given weapon that defines its basic behaviour in Destiny 2.
An Intrinsic Trait is, as the name suggests, an inherent part of a weapon and cannot be swapped out. Different Intrinsic Traits define the archetype of a weapon, which includes base impact and rate of fire, and are useful in determining what weapon is best for a given playstyle at a glance.
List of Intrinsic Traits
Bows have their own specific set of Intrinsic Traits.
Swords have their own specific set of Intrinsic Traits.
These Intrinsic Traits are unique to a certain weapon or selection of weapons outside of the weapon class-specific Traits.