[gdw]
The secondary sense ‘synod’ derives from a different etymology (synodus, cf. sene1). Medieval authors were probably unaware of a possible etymological/semantic differentiation between sene and sené, and on the basis of form, the unetymological sense is included in this entry.
The expression seint sené celestien (S Edm Life ants 2516) is included here in analogy with the sense ‘member of the heavenly senate’ sub senatur (from senatus), but may very well be read without the accent, in which case the phrase would be interpreted as ‘heavenly synod’ and belong sub sene1 (from synodus).