† seroObs. [L., adv. of sērus late.] Late; also, a late boy (at school). 1682Rec. Scott. Cloth Manuf. New Mills (S.H.S.) 17 And if the clerk be sero or absent to pay the double.1734T. Watt Vocab., Lang. School 8 What will you do to me? I'll set you up Amongst the Sero's.