In TeXForm#
TeXForm parses this entry as a character leaf mapped to U+03C4 (GREEK SMALL LETTER TAU).
\bbalpha\bbbeta\bbchi\bbdelta\bbDelta\bbdotlessi\bbdotlessj\bbepsilon\bbeta\bbgamma\bbGamma\txtbfbbtau
\txtbfbbtauSymbol
The τ symbol (Greek small letter tau, U+03C4), written as \txtbfbbtau in LaTeX text mode.