I found the following interpretation of thurisaz in this wonderful site.http://realmagick.com/articles/73/2173.html
This is not a safe rune, nor one to be trifled with. The jotnar represent natural forces usually hostile to humans. Thor is always killing them to keep the Nine Worlds safe for Gods and Humans. They have their own World called Jotunheim. This isn't a destination I'd recommend to the beginning pathworker! Both the Old Norwegian Rune Rhyme and the Old Icelandic Rune Poem have kept the original meaning of the rune, although the name changed slightly, to "Thurs," and stress the rune's special dangers for women, who should handle it with special care, and not anywhere near their menstrual period. The Old English Rune Poem, however, perhaps under Christian influence and probably inspired by the rune's shape, changed its name to "thorn" which meant the same then as it meant then. Hostile Fire and Frost Giants. Ogres. Trolls. Nasty sharp thorns. You get the picture. This is the rune of wildfire (Kenaz/Kaunaz is controlled fire). It is also the rune of pain, harm, hostility, explosion, enemies, firearms, and conflict. It relates to division and arguments. Injuries fall under Thurisaz, as do separation, passion, anger, uncontrolled emotions, and volcanos. Imagine how the Icelandic settlers felt when they realized they had burned their bridges behind them so to speak and moved onto an island with a Thurisaz-Rune at its heart. This is by no means a healing rune!
This rune can indicate harmful obsessions, including sexual ones. Remember that when the Giantess of the frozen Earth, Gerd refused Frey's proposal of marriage, his servant Skirnir carved three Thurisaz runes on a stick and threatened her with "longing, lust and madness". She then prudently reconsidered his offer, and lived happily ever after. On a more positive note, it can denote the will or motivation to make a change. Disaster, seen and used properly, can promote growth as well as destruction! Thurisaz' effects are at their worst when they are not seen and acknowledged. It often works in a hidden fashion, but seeks to break through to the surface by any available path - just like volcanic magma.
Handled carefully, this rune can be a useful addition to the wards of one's home. They can be set to grab hold of any hostile magick directed against you, shred, mutilate and mutate it (thorns, remember), up its volume, so to speak, and send it home to torment its maker! The worse the sending, the worse the comeuppance to its sender.
The legends of Thor and his battles with the jotnar (plural of jotun) can give further insights into this rune. Bear in mind that Thor is far from stupid. After all, to be a God, he'd have to be at least as smart as the smartest human. Rather, Thor is possessed of an unusual sort of cunning.
My own personal revelations concerning this rune, however, have come from work with Odin. This rune can be used, in emergencies, to assault an evildoer's fetch out on the "astral plane". It can cause insanity and even symptoms of possession. I believe Freya Aswynn has used this rune with similar results. Such a work, if undertaken at all, is obviously for an experienced runeworker who is absolutely sure that the need is great and that he or she is in the right.
Be careful with this rune. It is perhaps the most difficult and potentially most dangerous in the entire futhark. Only a strong will can control its forces. A weak will it will control! It can dredge up fiery rage, selfishness and stubbornness from a person's subconscious. Its energy can be used to control mobs, but at the same time it can fuel marches and demonstrations for much-needed change. Thurisaz is a war rune, with ties to Tyr and to Iron (used to make weapons).
Thurisaz is not "evil" in the Christian sense. It is a necessary part of the Futhark. But neither is it "sweetness and light" either. Bear this in mind when you begin to work with it, for sooner or later, the runeworker must deal with Thurisaz.
From the poetic Pam C. comes this Zen-like and obliquely blunt (figure that!) comment on the Rune Thurisaz:
"...PMS it's like a thurs slipped up my ass!" Note from Jordsvin: Ouch! and if you take the Rune name "thurs" literally as "(frost) giant," it hurts even worse. I don't think sex with a Thurs would be much fun for the human partner