What are some good defensive or "passive" shouts?

Become Ethereal
Whirlwind Sprint
Unrelenting Force (does not deal direct damage)
Aura Whisper

others?

Best defense is a good offense - Slow Time comes in handy for hack and slash and spell casting.

Animal Allegiance/Kyne's Peace.

Ah! Forgot about Slow Time.

Throw Voice

That was what I meant by Whisper.

Disarm.

I got those confused too at one point. They are both Defensive and Offensive depending on how you use them.

I might be the only one, but I kind of like Ice Form. I should quantify that - Ice Form is good for my 2-handed melee tank - mostly because certain mages can be a real PITA throwing 50-100point nukes at me every 1/2 second while I try to close range. Ice Form lets me paralyze them long enough to close the gap and start pounding on them hard, or maybe to heal up or use pots. It also has a bit of an AoE - I can sometimes hit 3 or 4 enemies with it if they'll cluster together.

I don't know if that would be considered offensive or defensive - it tends to be sort of both.

On my Mage Character, I thought Ice Form was a bit useless, so, it depends on your character build to some extent.