Two superset signs stacked vertically, a rare set theory relation.
U+2AD5SUBSET ABOVE SUBSETU+2AD7SUPERSET BESIDE SUBSETU+2AD4SUPERSET ABOVE SUBSETU+2AD8SUPERSET BESIDE AND JOINED BY DASH WITH SUBSETU+2AD3SUBSET ABOVE SUPERSETU+2AD9ELEMENT OF OPENING DOWNWARDSU+2AD2CLOSED SUPERSET OR EQUAL TOU+2ADAPITCHFORK WITH TEE TOPU+2AD1CLOSED SUBSET OR EQUAL TOU+2ADBTRANSVERSAL INTERSECTIONU+2AD0CLOSED SUPERSETU+2ADCFORKING256 characters in the Supplemental Mathematical Operators Unicode block, from number 215.
U+2AD6SUPERSET ABOVE SUPERSETU+2AD7SUPERSET BESIDE SUBSETU+2AD8SUPERSET BESIDE AND JOINED BY DASH WITH SUBSETU+2AD9ELEMENT OF OPENING DOWNWARDSU+2ADAPITCHFORK WITH TEE TOPU+2ADBTRANSVERSAL INTERSECTIONU+2ADCFORKINGU+2ADDNONFORKINGU+2ADESHORT LEFT TACKU+2ADFSHORT DOWN TACKU+2AE0SHORT UP TACKU+2AE1PERPENDICULAR WITH SU+2AE2VERTICAL BAR TRIPLE RIGHT TURNSTILEU+2AE3DOUBLE VERTICAL BAR LEFT TURNSTILEU+2AE4VERTICAL BAR DOUBLE LEFT TURNSTILEU+2AE5DOUBLE VERTICAL BAR DOUBLE LEFT TURNSTILEU+2AE6LONG DASH FROM LEFT MEMBER OF DOUBLE VERTICALU+2AE7SHORT DOWN TACK WITH OVERBARU+2AE8SHORT UP TACK WITH UNDERBARU+2AE9SHORT UP TACK ABOVE SHORT DOWN TACKU+2AEADOUBLE DOWN TACKU+2AEBDOUBLE UP TACKU+2AECDOUBLE STROKE NOT SIGNU+2AEDREVERSED DOUBLE STROKE NOT SIGNU+2AEEDOES NOT DIVIDE WITH REVERSED NEGATION SLASHU+2AEFVERTICAL LINE WITH CIRCLE ABOVEU+2AF0VERTICAL LINE WITH CIRCLE BELOWU+2AF1DOWN TACK WITH CIRCLE BELOWU+2AF2PARALLEL WITH HORIZONTAL STROKEU+2AF3PARALLEL WITH TILDE OPERATORU+2AF4TRIPLE VERTICAL BAR BINARY RELATIONU+2AF5TRIPLE VERTICAL BAR WITH HORIZONTAL STROKEU+2AF6TRIPLE COLON OPERATORU+2AF7TRIPLE NESTED LESS-THANU+2AF8TRIPLE NESTED GREATER-THANU+2AF9DOUBLE-LINE SLANTED LESS-THAN OR EQUAL TOU+2AFADOUBLE-LINE SLANTED GREATER-THAN OR EQUAL TOU+2AFBTRIPLE SOLIDUS BINARY RELATIONU+2AFCLARGE TRIPLE VERTICAL BAR OPERATORU+2AFDDOUBLE SOLIDUS OPERATORU+2AFEWHITE VERTICAL BARU+2AFFN-ARY WHITE VERTICAL BAR