Yes, there are several ways to do this.......
1. Use 'plines' and assign a width to them, or use pedit to make the 'line' a pline prior to doing the width. This isn't specifically lineweight but will produce the same idea.
2. Draw the line, select it and use the 'lineweight toolbar' to assign a line weight.
3. Move the linework onto a layer and assign that layer a certain color that corresponds to a pen color setting in your color table (ctb file) to print thicker then others. ie: set magenta to print with a 0.7 size rather then the default 0.25 pen width). Again, this isn't specifically line weight but will produce the same idea.
4. Move the linework onto a layer and assign a line weight to that layer itself, making sure the lineweight of that entity is set to 'bylayer'.