Adjective
capable of being stopped
Source: WordNetif we pick up our pace he may be stoppable Source: Internet
On instruments with stoppable strings, such as the violin or guitar, the player can shorten the vibrating length of the string, using their fingers directly (or more rarely through some mechanical device, as in the nyckelharpa and the hurdy-gurdy). Source: Internet
Some zithers combine stoppable (melody) strings with a greater number of "open" harmony or chord strings. Source: Internet