Any situation that is certain to end in failure or in which any favourable outcome is impossible.

(US, especially of a financial instrument) Sold directly to a customer without a sales commission. / (electricity) Not supplying power; open-circuited.

(US, finance) A financial instrument that is sold directly to a customer without a sales commission.

Now is an appropriate time to take a particular action.

(emphatic) I don't know. / Indicates that the speaker is completely ambivalent about something.

Speaking, promising, or boasting much, but doing little.

(idiomatic) All or nothing. Probably derived from "shoot duck or no dinner".

(aviation) The point in an aircraft's flight when there is insufficient fuel to reverse direction and return to the place of origin.

(vulgar, colloquial, sarcastic, somewhat derogatory) A riposte to someone who has just said something obvious

Opportunities will not wait; action should be undertaken without delay.