Strategic weaponry
Strategic weaponry reffers to large-scale weapons which can be used to decicively change the course of a conflict. These can mean different things in different venues.
On the Ground
In ground-based combat, strategic weapons most often refers to Nuclear Ordnance, more specifically the N1.5 varriant that can render very large portions of a country completely uninhabitable.
Space
In space, it most often--but not always--reffers to the Nova Bomb. Though mainly known for it's ability to destroy a star or planet, Nova weapons can actually be used in space much the same way hydrogen bombs or employed on a planet: to render large areas temporarily uninhabitable. The risidual heat and radiation from a Nova detonation in open space will typically be too much for the standard shielding of most vessels. This can effectively cordon off a portion of space for days or even weeks.
Other
The term is often used in reference to an over-all strategy, where part of the plan involves forcing the enemy to make a certain move. Somtimes only the threat of strategic weaponry is used, other times the weapons themselves are aimed at seemingly inconsequential targets as a show of force or to drive the enemy into a more advantagous location.