<u3 is an expansion to the popular <3 (heart). The addition of the letter 'u' shows the recipient that they are in your heart.

Mike: <u3
Nora: Awww <3333333

<u3 means your in my heart

i love you nicole

frankie: hey <u3

nicole: <u3 too.

U3

crapware found pre-installed in some USB flash drives. it is supposed to be a useful launch pad for portable applications, but instead quickly becomes an annoyance, asking for passwords, bugging down the process, and taking up space.

man, this U3 software sucks, get me a real flash drive