What does "combine" mean?

Additional senses

1. 2.To form a union; to agree; to coalesce; to confederate. You with your foes combine, And seem your own destruction to design Dryden. So sweet did harp and voice combine. Sir W. Scott.
2. 3.To unite by affinity or natural attraction; as, two substances, which will not combine of themselves, may be made to combine by the intervention of a third.
3. 4.(Card Playing) In the game of casino, to play a card which will take two or more cards whose aggregate number of pips equals those of the card played. Combining weight (Chem.), that proportional weight, usually referred to hydrogen as a standard, and for each element fixed and exact, by which an element unites with another to form a distinct compound. The combining weights either are identical with, or are multiples or multiples of, the atomic weight. See Atomic weight, under Atomic, a.