retrasar
/retɾaˈsaɾ/ · B1 · verb
to delay, to set back, to slow down, to postpone, to retard, to hold up, to put back
🐌⏳ re- (back) + tras (behind) = push something back behind schedule
Tras means behind, as in atrás (backwards). Retrasar pushes something back in time: retrasar la reunión = postpone the meeting. The noun un retraso is a delay, so el tren lleva retraso means the train is running late.