Used attributively to describe something arranged one behind another or functioning together.
Definitions
Arranged one behind the other or designed to be used by two in sequence. The research team installed a tandem solar cell to improve efficiency.
Less common modern usage, typically meaning 'together' or 'one behind another', e.g. 'to ride tandem'.
Definitions
Together; one directly after another in sequence. The cyclists pedalled tandem along the riverbank.
Synonyms
in concert
in conjunction
side by side
as one
in cooperation