Same entry in Eudemus and the Lexica Segueriana; a longer one in Photius s.v., with two further glosses (τιμᾳ̂ , προσεύχεται ).
The headword itself is third person singular, present indicative active, of ἀγάλλω (cf. under alpha 131), evidently quoted from somewhere. The possibilities include Pindar, Nemeans 5.43, and Euripides, Hercules 379.
The verb is used especially of what one does to a deity: see LSJ (web address 1).