someone who stands in front of a group of musicians or singers and directs their playing or singing
2 British EnglishTT
someone whose job is to collect payments from passengers on a bus
3 American EnglishTTT
someone who is in charge of a train and collects payments from passengers or checks their tickets [= guard British English]
something that allows electricity or heat to travel along it or through it: ➔ lightning conductor
Wood is a poor conductor of heat.