Tr2tog

Treble crochet 2 together is one stitch decrease. Yarn over 2 times, insert hook in stitch, yarn over and pull up a loop, yarn over and draw through 2 loops twice, yarn over 2 times, insert hook in next stitch, yarn over and pull up a loop, yarn over and draw through 2 loop twice, you should have 3 loops on hook, yarn over and draw through remaining 3 loops.

Tr2tog