April 15, 2015, is the last day to file your 2011 tax return to claim a refund; if you had an extension, your deadline is October 15, 2015.
A slide is a piece of glass on which you put something that you want to examine through a microscope. ...a drop of blood on a slide. A slide is a piece of playground equipment that has a steep slope for children to go down for fun. ...two young children playing on a slide. COBUILD Advanced English Dictionary.
Slipping means that surfaces slide with respect to each other--there is relative motion between the surfaces. There may or may not be friction. If there is no slipping, then the surfaces do not slide at the point of contact. There may or may not be friction involved.