There are multiple definitions - click on the translation that matches your context.

sound means:

sólido

adjetivo

full

sound

adjective

"Situação financeira sólida" = sound financial situation/status.

in good condition; not damaged or injured

The goods were in sound condition.

reliable; effective; complete or thorough

He was a sound employee.

showing good judgment; able to be trusted

The judgment was sound.