at second hand by hearsay rather than direct observation or experience.

get your second wind: gain a new strength or energy to continue something that is an effort.

have a second string to your bow: seestring.

on second thoughts having reconsidered a matter (and arrived at a different opinion or decision).

☞ US English also uses on second thought.

play second fiddle to: seefiddle.

second banana: seebanana.

second childhood a state of childishness that sometimes occurs in old age.

second nature a characteristic or habit in someone that appears to be instinctive because that person has behaved in a particular way so often.

a second thought a moment's further consideration; any worry or concern.

second to none surpassed by no other.

1961Joseph HellerCatch-22 He would stand second to none in his devotion to country.