401-k plan: a retirement savings plan that is funded by employee contributions and (often) matching contributions from the employer; contributions are made from your salary before taxes and the funds grow tax-free until they are withdrawn, at which point they can be converted into an IRA; funds can be transferred if you change employers and you can (to some extent) manage the investments yourself
pension plan: a plan for setting aside money to be spent after retirement
bacitracin: a polypeptide antibiotic of known chemical structure effective against several types of Gram-positive organisms; usually applied locally