SPONTANEITY, SPONTANEOUS, SPONTANEOUSLY
ADJECTIVES
1637 ► ULTRONEOUS made, offered, etc., of one’s own accord; spontaneous, voluntary
1895 ► BALDHEADED completely unprepared; utterly spontaneous → US sl.
1980 ► RANDOM spontaneous, unexpected → US students’ & teen sl.
ADVERBS
1375 ► OF ONE’S OWN HEAD out of one’s own thought, device, or will; of one’s own accord, spontaneously → obs.
1627 ► ULTRONEOUSLY of one’s own accord; spontaneously, voluntarily
1970 ► OFF THE WALL spontaneously, unconventionally → US sl.
NOUNS
1623 ► ULTRONEOUSNESS voluntary action; spontaneity → rare
VERBS
1960 ► PLAY IT BY EAR to act in an ad hoc manner; to behave spontaneously → sl.
1960 ► PLAY IT BY SKYHOOK to act in an ad hoc manner; to behave spontaneously → sl.
Lexicophilia 