`ubrace` (unary)
Ubrace
AsciiMath
ubrace(x)
LaTeX
\underbrace{x}
MathML
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
<mstyle displaystyle="true">
<munder>
<mi>x</mi>
<mo>⏟</mo>
</munder>
</mstyle>
</math>
OMML
<m:oMathPara>
<m:oMath>
<m:limLow>
<m:limLowPr>
<m:ctrlPr>
<w:rPr>
<w:rFonts w:ascii="Cambria Math" w:hAnsi="Cambria Math"/>
<w:i/>
</w:rPr>
</m:ctrlPr>
</m:limLowPr>
<m:e>
<m:r>
<m:t>x</m:t>
</m:r>
</m:e>
<m:lim>
<m:r>
<m:t>⏟</m:t>
</m:r>
</m:lim>
</m:limLow>
</m:oMath>
</m:oMathPara>