's TERMinal INFOrmation
Technically superior to its predecessor, termap, it used a hierarchical database of binary files - one per terminal described. The accompanying C library incorporated minor differences from that with termcap, providing sundry annoying incompatibilities.
The binary descriptions could be decompiled (by untic) into human-readable text forms, with "meaningful" capability names. This text form could then be amended and recompiled (by tic) to effect changes to the database.
Since the arrival of ncurses, terminfo has been the preferred terminal description format for open source software.