IPA: /kəʊˈtɜːmɪnəsli/
KK: /kəʊˈtɜːrmɪnəsli/
In a way that shares the same boundaries or limits with something else.
The two projects were developed coterminously, ensuring they complemented each other perfectly.
Coterminously → It is formed from "co-" (meaning together) and "terminus" (from Latin, meaning boundary or limit) and the suffix "-ly" (meaning in a manner). The word describes two or more things that share the same boundary or limit, occurring together in time or space.
Think of things that are 'together' ('co-') at the same 'boundary' ('terminus') — that's why coterminously means occurring at the same limits.