|Offensive/Defensive feline posture - Photo by Demond Handy on Flickr|
However, this cat does not look overly defensive to me and the dog is quite passive, not knowing what to do next. The pupils of the cat's eyes are not dilated but constricted. Dilated pupils indicate a defensive threat posture. He is looking at the dog and looks calm and not fearful and ready to defend himself. Perhaps his behavior is between defense and attack.
Offensive threat posture
A cat shows:
- hairs raised along back (piloerection);
- back legs extended;
- ears drawn back (to protect them);
- cat looks directly at the opponent;
- pupils are constricted;
- tail held down pointing towards ground and not tucked under. Tip of tail may be "flagging" slowly.
Defensive threat posture
A cat shows:
- hairs standing up on his back;
- square on: cat presents himself towards the other animal with "arched lateral display" (an attempt to look larger);
- a defensive facial expression reflecting his state of mind (contradicting the attempt to look larger);
- ears flattened and whiskers drawn back;
- teeth bared by corners of mouth being drawn back;
- pupils of eyes are dilated;
- tail is erect or concave - tip pointed down.
Refs: The Cat Its Behavior Nutrition & Health page 139 - ISBN 978-0-8138-0331-9 (the quote is from this excellent book)