LCI
Loaded Chamber Indicator — a visual or tactile feature that signals whether a round is in the chamber.
Also: loaded chamber indicator
An LCI lets the user verify chamber state without retracting the slide — typically a small protrusion on the extractor that pops up when a round is chambered, or a viewing port. Some jurisdictions (notably California and Massachusetts) require LCIs on commercial handguns. An LCI is a convenience, not a substitute for a press check — never trust your life to a sliver of metal.