An isolation suit was a type of stealth clothing used by the Federation Starfleet in the 24th century. The suit was equipped with technology which made the person wearing it practically invisible. It was possible to see through the invisibility when a person wearing the suit was viewed through a screen in a "duck blind" monitoring station. Starfleet used isolation suits when observing pre-warp civilizations in order to prevent cultural contamination, in accordance with the Prime Directive. (Star Trek: Insurrection)
In the script of Star Trek: Insurrection, the term cloaked is used of the people using the suits and the term decloaking is used when isolation suits are turned off, but it is also clearly indicated that a force field is responsible for the invisibility.