zatrovati

1. (of water, soil, animals) to poison
   Neko je zatrovao komšijinog psa. — Someone poisoned the neighbour's dog.
   Fabrika je zatrovala reku i okolna polja. — The factory poisoned the river and the surrounding fields.
2. (of relations, atmosphere) to poison; to sour
   Ta svađa je zatrovala odnose u celoj porodici. — That quarrel soured relations in the whole family.

For poisoning a person, otrovati is more usual.