(idiomatic, in similes) To attempt to control the uncontrollable. / Used other than figuratively or idiomatically: see herd, cat.

(sociology) the tendency of a group of individuals (a herd) to react coherently without there being any coordination between them. The term may be applied to animals, or to human phenomena such as stock market bubbles and behaviour in political demonstrations.

(sociology) herding instinct.

(transitive, idiomatic, US) To supervise a group of people and their work.

(sports) A non-official path created by hikers, and usually maintained by the hikers themselves.

(epidemiology) The indirect protection against the spread of a contagious disease in a given population caused by the immunity of a significant proportion of the population to that particular disease; the immunity may have been obtained through having survived the infection or through vaccination.

A stud boar, a male pig kept for breeding.

(slang, transitive) To attack a person as a group or gang.

plural of thundering herd problem

(computing theory) The undesirable situation where a large number of processes waiting for an event are awoken whenever the event occurs, and then engage in a conflict over which process handles the event.