Tre corde
In piano music, this is a direction to release the una corda pedal.
The effect is a full sound since all of the strings are being struck.
Reference
Grove Music Online. "Violin Family." Oxford Music Online. Accessed January 26, 2025. https://www.oxfordmusiconline.com/grovemusic/display/10.1093/gmo/9781561592630.001.0001/omo-9781561592630-e-0000028298.