The word posaste is the preterite form of posar in the second person singular. There are other translations for this conjugation.
See the full posar conjugation

posar

Estoy de acuerdo, posaste como un santo y viniste a mí.
I agree. You posed as a saint and came to me.
¿Alguna vez posaste para un artista?
Have you ever posed for an artist?
¿No posaste para la cámara?
Didn't you pose for the camera?
Dile que posaste para ella.
Tell him you posed for it.
Como lo llevabas la primera vez que posaste para mí.
The way it fell the first day I asked you to pose for me.
No posaste para ellas.
You didn't sit for them.
Pero tú no posaste, no?
But you didn't pose, did you?
Posaste para él, ¿verdad?
You did pose for it, didn't you?
¿Posaste para esta foto? Te ves airoso y misterioso.
Did you pose for this picture? You look graceful and mysterious.
Para una nueva sesión de fotos posaste con dos mujeres.
For a new photo-session you posed with two women.
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