It means immersion and the meaning of the baptism it is not only the death in Adam and the resurrection in Jesus, but even the meaning to purify ourselves from our sins.
Baptism is for the remission of the sins. .
Anyway the basin for the ablutions it has a lot to do with the baptism. Baptism was surely known to the Jews of the Christ's time. We have two scriptures to support this idea. And he saith, I am not. Make straight the way of the Lord, as said the prophet Esaias.