Freezing: attentive immobile state (complete absence of movement except respiration and tense body posture associated with a decreased heart rate) occurring at intermediate levels of threat allowing animals to avoid detection and to enhance perception. It is a universal fear response with variations between species (from Roelofs, 2017). 

Roelofs, K. (2017). Freeze for action: neurobiological mechanisms in animal and human freezing. Philosophical Transactions of the Royal Society B: Biological Sciences, 372, 20160206.