/ ˌθɪəˈretɪkl; NAmE ˌθiːə-/ adjective [ usually before noun ]
1.
concerned with the ideas and principles on which a particular subject is based, rather than with practice and experiment :
a theoretical approach
theoretical physics
The first year provides students with a sound theoretical basis for later study.
OPP experimental , practical
2.
that could possibly exist, happen or be true, although this is unlikely :
It's a theoretical possibility.
► the·or·etic·al·ly / -kli; NAmE / adverb :
theoretically sound conclusions
It is theoretically possible for him to overrule their decision, but highly unlikely.