The Collaborative International Dictionary
must \must\, musth \musth\(m[u^]st), a. [Hind. mast intoxicated, ruttish, fr. Skr. matta, p.p. of mad to rejoice, intoxicate.] (Zo["o]l.) Being in a condition of dangerous frenzy, usually connected with sexual excitement; -- said of adult male elephants which become so at irregular intervals, typicaly due to increased testosterone levels. -- n.
The condition of frenzy.
An elephant in must.
Wiktionary
n. A time during which male elephants exhibit increased levels of sexual activity and aggressiveness.
WordNet
n. an annual phase of heightened sexual excitement in the males of certain large mammals (especially elephants); is associated with discharge from a gland between the eye and ear; "the frenzied elephant was in musth"
Wikipedia
Musth or must (Urdu: مست) is a periodic condition in bull (male) elephants, characterized by highly aggressive behavior and accompanied by a large rise in reproductive hormones. Testosterone levels in an elephant in musth can be as much as 60 times greater than in the same elephant at other times. However, whether this hormonal surge is the sole cause of musth, or merely a contributing factor, is unknown. Scientific investigation of musth is problematic because even the most placid elephants become highly violent toward humans and other elephants during musth.
Usage examples of "musth".
I need a pick to clean out my musth gland, and those spindly things are just the right size.
Longtusk and a few others, mastodonts in musth and so prone to irritability.
Her posture was hard and still, as if she were a musth Bull challenging a younger rival.
Bull in musth, dribbling from his temple glands and trickling urine, emitted a powerful scent indeed.
And if one of them was in musth, and one of us in oestrus, there would be a mating.
For his first few musth seasons Thunder would simply be overpowered by the older, mature Bulls.
Dark fluid leaked from his musth glands and down his face, and he dribbled urine as he walked.
Although a male mammoth reached puberty around twelve, he did not begin musth until he was close to thirty, and then only for a week or so.
But, by the time he reached his late forties, and was in his prime, if he was in top condition, he could be in musth for three or four months each year.
When a female was in estrus, or a male was in musth, the pitch of their voices lowered.
Ayla could hear the low rumbles of the estrus female clearly enough, but the male in musth had such quiet-seeming deep tones that they barely heard him.
Besides lending male mammoths irresistible charm, to females, musth also conferred dominance over males, making them very aggressive even toward those who were larger, unless they were also in that excited state.
Only another musth bull would try to face him, and only if he was close to the same size.
The deep-toned calls and the pungent urine trails of the musth male did more than announce his presence to eager females, they also announced his location to other males.
Only three or four other bulls were in musth at the same time, during the six- or seven-month period that females might come into estrus, but it was unlikely that any of those who were also in lust would challenge the big russet for the female who was in heat.