Son Gokuu's ability to instantly teleport from place to the other, provided that he can recognise a qi pattern that is there possess a rather simple if verbose name.

時間がなくてよ 教えてもらった技はひとつだけなんだ そんでも えれえ 苦労したんだけどさ
瞬間移動ってやつが できるようになったぜ!

Jikan ga nakuteyo oshiete moratta waa wa hitotsu dake nan da sondemo eree kurou shitan dakedosa
Shunkanidou tte yatsu ga dekiruyou ni natta ze!

“Where there was nearly no more time, they taught me only one technique, that was after a damn rough bout of work.”
“I am able to use the Teleportation, y’see!”

(Volume 28, Dragon Ball by Toriyama)

Danish version:

Jeg har også lært en ny teknik, men den er temmelig genial.
Jeg behersker nu den Momentane Teleportation.

“I have also learned a new technique, but it is rather genius”
“I know master the Ephemeral Teleportation

(Volume 28, Dragon Ball – Drengen fra Fremtiden, translated by John Lysmand)

Its name is plainly the Japanese word for teleportation, shunkan idou (瞬間移動, lit. "instant movement"), and has for various reasons been mistranslated and localised into longer often nonsensical names.

"Ephemeral Teleportation," makes little sense, a teleportation is by is very nature instantaneous or ephemeral and as such its tautological to give it that extra adjective. The adjective momentan is rather rare in Danish, too, so presumably it is also for the sake of picking something arcane or mystical sounding. It itself equates as a Romance loan word whence English also gets its "momentary," albeit the regular Danish word is øjeblikkelig.

Does the official American English localisation "Instantaneous Transmission," merit any actual meaning?

No. It sounds sufficiently science-fiction'y, but "transmission" could literally refer to transmitting anything, and the name if anything sounds like a verbose explanation rather than a translation of the word "teleportation (shunkan idou)."

The Japanese wikipedia article on the topic of teleportation lists not only shunkan idou as the actual Japanese translation for this concept, but also the loan word terepôtêshon (テレポーテーション), literally from the same English word.

So, in short a needlessly verbose translation on a technique or word that already has an existing translation.