ETHERAL:
1 a : of or relating to the regions beyond the earth (WHICH ALSO INCLUDES OTHER DIMENSIONS)
c : unworldly, spiritual (NEED I EXPLAIN MORE OF ITACH'S SWORD CAPABILITIES HERE)
Also lets take into consideration another thing zetsu said in MANGA
ORO NEVER FOUND THE SWORD BECAUSE IT WAS A SPIRITUAL BLADE...IF YOU LOOK IN A DICTIONARY FOR THE MEANING OF ETHERAL YOU WILL ALSO SEE THAT THE SWORD COULD NOT BE SENSED...Sasuke fight vs Itachi He was unable to buss a single move in his defence...He was sealed immediately.
You must be registered for see images
How can Tobi Kamui or avoid an attack from a spiritual sword that cannot be sensed, which has no defined shape...All he sees is the Gourd the sword is in, not the sword itself.
You must be registered for see images
Any move Tobi uses against Itachi is reflected on himself instantly By the YATA mirror...Remember iTachi's Susanoo disappeared in the fight against sasuke, but as soon as sasuke threw the kunai, Susanoo appeared and reflected the aatack back.
This shows Itachi does not need to sustain susanoo he just uses it as a defence mechanism when needed....Infact he could have killed sasuke by reflecting his own Lightening on him with the YATA mirror....Goes to show what can happen if the HIDE-NO-JUTSU guy tries to even attack.
You must be registered for see images
I DID NOT SAY HE WAS INVINCIBLE...MADARA AND TOBI SLAVE/BODY (ZETSU) SAID SO....READ FOR YOUSELF AND STOP DENYING WHAT THE MANGA SAYS HEHEHE...DON'T YOU THINK ZETSU WOULD KNOW TOBI'S FULL STRENGTH?? ESPECIALLY BEING ATTACHED TO HIS BODY...Please don't say Zetsu hyped it up because he was talking to himself so there was no one to hype anything up to