Trifle, toy, dally, flirt, coquet can all mean to deal with a person or thing without seriousness, earnestness, close attention, or purpose.
Trifle , the most comprehensive term of the group, may be used interchangeably with any of the others, implying any of such varied attitudes as playfulness, unconcern, indulgent contempt, or light amorousness.
Toy implies a dealing with a person or thing in a way that keeps one pleasantly occupied but does not engage one’s full attention or evoke serious intention.
Dally stresses indulgence in something (as thoughts or plans) as a pastime or amusement rather than as leading to something definite or serious; it usually retains some hint of deliberate dawdling, the notion predominant in another of its senses.
Flirt , which in several of its senses implies quick jerky movement, in this extended use stresses vagrancy and superficiality of interest, attention, or liking and often a tendency to pass heedlessly from one person or concern to another.
Coquet primarily refers to a trifling in love, such as is characteristic of a flirtatious woman, but it is also used in reference to things which catch one’s interest but with which one will not come fairly to terms.