I could do that.
However, ‘one-shot’ or a variation on that line could refer to the fact that it can’t move and thus can only absorb a single star to be used for one or two attacks.
Perhaps “some kind of single charge Kyber cannon.” would make everyone happy.
Alternatively…perhaps we could play up the fact that this weapon is experimental and unstable:
“An extremely unstable Kyber cannon.”
or
“A massive, unstable Kyber cannon.”
or
“Some kind of unstable Kyber cannon.”
This would not only set up the plan later in the scene based around destabilizing the weapon, but it would explain the First Order’s behavior as well. Only Hux seems eager to use the weapon and his last dialogue in the film practically implies that he expected the weapon to be destroyed. It also explains why Snoke is nowhere near the Starkiller at any point in the film, and why such a weapon isn’t just a power-crept Death Star.