A.T. Robertson Commentary John 12:33

"But this he said, signifying by what manner of death he should die." — John 12:33 (ASV)

Signifying (σημαινων). Present active participle of σεμαινω, old verb to give a sign (σημειον) as in Ac 25:27, and the whole phrase repeated in 18:32 and nearly so in 21:19. The indirect question here and in 18:32 has the imperfect εμελλεν with present infinitive rather than the usual present μελλε retained while in 21:19 the future indicative δοξασε occurs according to rule. The point in ποιω (qualitative relative in the instrumental case with θανατω) is the Cross (lifted up) as the kind of death before Christ.