Liddell–Scott–Jones: συγκέντρωσις

συγκέντρωσις,εως,ἡ, Astron.,

A. a simultaneous relation of centres, i.e. when the sun's centre is at that point of the ecliptic which rises, sets, or culminates coincidently with the rising, etc., of a given star, Ptol. Alm. 8.5 (pl.).