(not-comparable) Number-two; following after the first one with nothing between them. The ordinal number corresponding to the cardinal number two.
(not-comparable) Next to the first in value, power, excellence, dignity, or rank; secondary; subordinate; inferior.
(not-comparable) Being of the same kind as one that has preceded; another.

Something that is number two in a series.
Something that is next in rank, quality, precedence, position, status, or authority.
The place that is next below or after first in a race or contest.
(plural-normally) A manufactured item that, though still usable, fails to meet quality control standards.
(plural-normally) An additional helping of food.
A chance or attempt to achieve what should have been done the first time, usually indicating success this time around. (See second-guess.)
The interval between two adjacent notes in a diatonic scale (either or both of them may be raised or lowered from the basic scale via any type of accidental).
The second gear of an engine.
Second base.
The agent of a party to an honour dispute whose role was to try to resolve the dispute or to make the necessary arrangements for a duel.
A Cub Scout appointed to assist the sixer.
(informal) A second-class honours degree.

(transitive) To agree as a second person to (a proposal), usually to reach a necessary quorum of two. (See etymology 3 for translations.)
To follow in the next place; to succeed.
To climb after a lead climber.

A unit of time historically and commonly defined as a sixtieth of a minute which the International System of Units more precisely defines as the duration of 9,192,631,770 periods of radiation corresponding to the transition between two hyperfine levels of caesium-133 in a ground state at a temperature of absolute zero and at rest.
A unit of angle equal to one-sixtieth of a minute of arc or one part in 3600 of a degree.
(informal) A short, indeterminate amount of time.

(UK, transitive) To transfer temporarily to alternative employment.
(transitive) To assist or support; to back.
(transitive) To agree as a second person to (a proposal), usually to reach a necessary quorum of two. (This may come from etymology 1 above.)
(transitive) To accompany by singing as the second performer.

One who supports another in a contest or combat, such as a dueller's assistant.
One who supports or seconds a motion, or the act itself, as required in certain meetings to pass judgement etc.
(obsolete) Aid; assistance; help.