When a person or animal pushs in between two or more people to try and 'fit in', making it awkward.
Person A: Blah blah
Person B: Blah blah
A shy person walks quickly towards them, and squeezes in between them, not talking, making it really awkward.
The Gillarder: *nothing*
Person B: Woah, you just got Gillarded.
Person A: So did you. AWKWARD.
Prices shown in USD.