A
AARO
All-domain Anomaly Resolution Office — the U.S. Department of Defense entity established in 2022 to detect, identify, and attribute unidentified anomalous phenomena across air, sea, space, and transmedium domains.
AATIP
Advanced Aerospace Threat Identification Program — the secretive U.S. Department of Defense unit that ran from 2007 to 2012, studying anomalous aerospace events for potential threat implications.
B
Belgian Wave
The 1989–1990 Belgian UFO sighting wave, featuring thousands of witness reports of large triangular craft and an officially-released military intercept report from the night of 30–31 March 1990.
Bracewell probe
A hypothetical autonomous interstellar probe sent by an extraterrestrial civilization to observe and possibly communicate with technological neighbors. Proposed by physicist Ronald Bracewell in 1960.
F
Fermi paradox
The apparent contradiction between the high estimated probability of extraterrestrial civilizations (per the Drake equation) and the absence of obvious evidence of contact. Named for physicist Enrico Fermi's 1950 lunchroom question: 'Where is everybody?'
FLIR
Forward Looking Infrared — a class of thermal-imaging sensor mounted on military aircraft and other platforms, used to detect heat signatures of objects against background. Many of the most-cited modern UAP videos are FLIR captures.
Foo fighter
World War II Allied aircrew slang for unidentified luminous objects observed accompanying military aircraft, particularly over the European and Pacific theaters in 1944–1945.
G
Ghost rocket
Sweden- and Scandinavia-centered reports of rocket-like flying objects observed in 1946, predating the Arnold sighting and constituting one of the first post-WWII waves of unidentified aerial phenomena.
Gimbal
The 2015 ATFLIR video captured by an F/A-18 from the USS Theodore Roosevelt, showing a smooth oblong object that appears to rotate. The Department of Defense confirmed the footage's authenticity in 2020.
N
NHI
Non-Human Intelligence — a term increasingly used in U.S. government UAP discourse to refer to any intelligence not of human origin, with deliberate breadth (terrestrial-but-non-human, extraterrestrial, interdimensional, etc.).
NUFORC
National UFO Reporting Center — a U.S. civilian sighting-report intake service founded in 1974, operating the most comprehensive public sighting database in North America.
P
Project Blue Book
The U.S. Air Force's primary UFO investigation program from 1952 to 1969, which examined 12,618 reports and concluded that 701 remained 'unidentified' after investigation.
Project Grudge
The second U.S. Air Force UFO investigation program (1949–1951), characterized by an overtly skeptical institutional posture, and the bridge between Project Sign and Project Blue Book.
Project Mogul
A classified U.S. Army Air Forces program (1947–1949) using high-altitude balloon trains to detect Soviet atmospheric nuclear tests via long-range acoustic monitoring. Identified as the source of the 'Roswell incident' debris in the 1994 USAF Roswell Report.
Project Sign
The first U.S. Air Force UFO investigation program, operating from 1948 to early 1949 in response to the post-WWII surge in unidentified aerial sightings.
U
UAP
Unidentified Anomalous Phenomena (formerly Unidentified Aerial Phenomena) — the U.S. government's preferred term for what was historically called UFOs, deliberately broader to include maritime, space, and transmedium objects.
UFO
Unidentified Flying Object — the older, original term for anomalous aerial phenomena, in U.S. government usage from approximately 1952 until replacement by 'UAP' in 2021.