through-conjugation 

https://doi.org/10.1351/goldbook.08214
Phenomenon whereby electrons can be delocalized from any of three (or more) groups to any other.

Example: p-XCA6HA4Y, where an electron pair can be delocalized from electron-donating X not only to ring carbons but also to electron-withdrawing Y.

Note 1: This may be contrasted with cross-conjugation.

Note 2: In Hammett-type correlations (linear Gibbs-energy relationships), this situation can lead to exalted substituent constants σ+ or σ, as in solvolysis of p-CHA3OCA6HA4C(CHA3)A2Cl or acidity of p-nitrophenol, respectively.

Source:
PAC, 2022, 94, 353. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 2021)) on page 518 [Terms] [Paper]