In my experience, departments, buildings and school districts working towards consistent grading practices benefit from establishing common grading guidelines or beliefs.  For example, in my current school district, instead of merely saying "we use standards-based grading," we have agreed to utilize the following grading guidelines: 
  1. Entries in the grade book that count towards the final grade will be limited to course or grade level standards.**
  2. Extra credit will not be given at any time.
  3. Students will be allowed multiple opportunities to demonstrate their understanding of classroom standards in various ways. Retakes and revisions will be allowed.
  4. Teachers will determine grade book entries by considering multiple points of data emphasizing the most recent data and provide evidence to support their determination.
  5. Students will be provided multiple opportunities to practice standards independently through homework or other class work. Practice assignments and activities will be consistent with classroom standards for the purpose of providing feedback. Practice assignments, including homework, will not be included as part of the final grade.
** Exceptions will be made for midterm and/or final summative assessments. These assessments, limited to no more than one per nine-week period may be reported as a whole in the grade book.

For those interested, a look at related scholarly literature yields several definitions:

One grading practice that is gaining popularity is standards-based grading, which involves measuring students' proficiency on well-defined course objectives (Tomlinson & McTighe, 2006). Although many districts adopt standards-based grading in addition to traditional grades, standards-based grading can and should replace traditional point-based grades.

Scriffiny, P.L. (2008). Seven reasons for standards-based gradingEducational Leadership, 66(2), 70-74.

Standards-based grading (SBG) is an approach to assessment and reporting in which scores are attached to the specific learning objectives of a course, rather than to assignments or tests. Each score represents a student’s mastery of that learning objective, and may change over time in response to evidence that her level of understanding has changed.

Beatty, I. (2013). Standards-based grading in introductory university physics. Journal of the Scholarship of Teaching and Learning, 13(2), 1-22 [PDF]
Standards-based grading connects student grades to specific learning objectives, provides students with direct and specific information to guide their study, and often involves less grading time for the instructor than traditional methods do.
Duker, P, Gawboy, A, Hughes, B, & Shaffer, K.P. (2015) Hacking the music theory classroom: Standards-based grading, just-in-time teaching, and the inverted class. Music Theory Online, 21(2). [Available online]

The goal of Standards-Based Grading (SBG) is to measure a student’s progress towards
achievement of a standard, and thus to show what students are able to do. Students have multiple opportunities to demonstrate their achievement of the standard, and the final grade is based on the student’s overall mastery of the standard by the end of the term, not a weighted average of material throughout the term. Standards-Based Grading can also help instructors to more clearly communicate to the students exactly what they will be expected to know and demonstrate on assessments.

Post, S.L. (2014). Standards-Based Grading in a Fluid Mechanics Course. Paper presented at the 121st ASEE Annual Conference & Exposition, Indianapolis, IL. [Available online]

...and one of my personal favorites:

Traditional Grading SystemStandards-Based Grading System
1. Based on assessment methods (quizzes, tests, homework, projects, etc.). One grade/entry is given per assessment.1. Based on learning goals and performance standards. One grade/entry is given per learning goal.
2. Assessments are based on a percentage system. Criteria for success may be unclear.2. Standards are criterion or proficiency-based. Criteria and targets are made available to students ahead of time.
3. Use an uncertain mix of assessment, achievement, effort, and behavior to determine the final grade. May use late penalties and extra credit.3. Measures achievement only OR separates achievement from effort/behavior. No penalties or extra credit given.
4. Everything goes in the grade book – regardless of purpose.4. Selected assessments (tests, quizzes, projects, etc.) are used for grading purposes.
5. Include every score, regardless of when it was collected. Assessments record the average – not the best – work.5. Emphasize the most recent evidence of learning when grading.

Adapted from O’Connor K (2002).  How to Grade for Learning: Linking grades to standards (2nd ed.). Thousand Oaks, CA: Corwin Press.