an imaginary line around which a turning object spins

point around which something revolves

the most interesting, intense, violent, energetic etc part (of an event, game, speech, storm etc)

peak, culmination

an uncertain event (especially one causing problems)

chance happening; possibility

a turning point in an illness, life, history

critical situation

a place where two or more roads meet

intersection

(in the event of) a serious and dangerous happening or situation needing quick action

crisis, danger

a central pin or point on which something turns; something on which an argument or discussion depends

center point about which something

a narrow passage of water connecting two seas; trouble; difficulty

crisis, difficulty

(an act of) changing, from one condition or set of circumstances to another

change, often major